Positive resist composition and method of forming resist pattern

ABSTRACT

A positive resist composition including a base component (A) which exhibits increased solubility in an alkali developing solution under action of acid and an acid-generator component (B) which generates acid upon exposure, the base component (A) including a polymeric compound (A1) containing a structural unit (a0) represented by general formula (a0-1), a structural unit (a1) derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group, and a structural unit (a3) derived from an acrylate ester containing a hydroxy group-containing aliphatic hydrocarbon group represented by general formula (a3-1), and the amount of the structural unit (a3) based on the combined total of all structural units constituting the polymeric compound (A1) being in the range of 1 to 30 mol %.

This application is a Divisional of U.S. application Ser. No.12/591,819, filed Dec. 2, 2009 now U.S. Pat. No. 8,236,477.

TECHNICAL FIELD

The present invention relates to a positive resist composition and amethod of forming a resist pattern using the resist composition.

Priority is claimed on Japanese Patent Application No. 2008-309850,filed Dec. 4, 2008, and Japanese Patent Application No. 2009-130554,filed May 29, 2009, the contents of which are incorporated herein byreference.

BACKGROUND ART

In lithography techniques, for example, a resist film composed of aresist material is formed on a substrate, and the resist film issubjected to selective exposure of radial rays such as light or electronbeam through a mask having a predetermined pattern, followed bydevelopment, thereby forming a resist pattern having a predeterminedshape on the resist film.

A resist material in which the exposed portions become soluble in adeveloping solution is called a positive-type, and a resist material inwhich the exposed portions become insoluble in a developing solution iscalled a negative-type.

In recent years, in the production of semiconductor elements and liquidcrystal display elements, advances in lithography techniques have leadto rapid progress in the field of pattern miniaturization.

Typically, these miniaturization techniques involve shortening thewavelength of the exposure light source. Conventionally, ultravioletradiation typified by g-line and i-line radiation has been used, butnowadays KrF excimer lasers and ArF excimer lasers are starting to beintroduced in mass production. Furthermore, research is also beingconducted into lithography techniques that use an exposure light sourcehaving a wavelength shorter than these excimer lasers, such as F₂excimer lasers, electron beam, extreme ultraviolet radiation (EUV), andX-ray.

Resist materials for use with these types of exposure light sourcesrequire lithography properties such as a high resolution capable ofreproducing patterns of minute dimensions, and a high level ofsensitivity to these types of exposure light sources.

As a resist material that satisfies these conditions, a chemicallyamplified composition is used, which includes a base material componentthat exhibits a changed solubility in an alkali developing solutionunder the action of acid and an acid generator that generates acid uponexposure.

For example, a chemically amplified positive resist contains, as a basecomponent (base resin), a resin which exhibits increased solubility inan alkali developing solution under action of acid, and an acidgenerator is typically used. If the resist film formed using the resistcomposition is selectively exposed during formation of a resist pattern,then within the exposed portions, acid is generated from the acidgenerator, and the action of this acid causes an increase in thesolubility of the resin component in an alkali developing solution,making the exposed portions soluble in the alkali developing solution.

Currently, resins that contain structural units derived from(meth)acrylate esters within the main chain (acrylic resins) are nowwidely used as base resins for resists that use ArF excimer laserlithography, as they exhibit excellent transparency in the vicinity of193 nm (for example, see Patent Document 1). Here, the term“(meth)acrylic acid” is a generic term that includes either or both ofacrylic acid having a hydrogen atom bonded to the α-position andmethacrylic acid having a methyl group bonded to the α-position. Theterm “(meth)acrylate ester” is a generic term that includes either orboth of the acrylate ester having a hydrogen atom bonded to theα-position and the methacrylate ester having a methyl group bonded tothe α-position. The term “(meth)acrylate” is a generic term thatincludes either or both of the acrylate having a hydrogen atom bonded tothe α-position and the methacrylate having a methyl group bonded to theα-position.

Further, in order to improve various lithography properties, a baseresin having a plurality of structural units is currently used for achemically amplified resist. For example, in the case of a positiveresist, a base resin containing a structural unit having an aciddissociable, dissolution inhibiting group that is dissociated by theaction of acid generated from the acid generator, a structural unithaving a polar group such as a hydroxyl group, a structural unit havinga lactone structure, and the like is typically used. Among thesestructural units, a structural unit having a lactone structure isgenerally considered as being effective in improving the adhesionbetween the resist film and the substrate, and increasing thecompatibility with an alkali developing solution, thereby contributingto improvement in various lithography properties.

DOCUMENTS OF RELATED ART Patent Document

-   [Patent Document 1] Japanese Unexamined Patent Application, First    Publication No. 2003-241385-   [Patent Document 2] Japanese Unexamined Patent Application, First    Publication No. 2006-016379

SUMMARY OF THE INVENTION

As further progress is expected to be made in lithography techniques andthe application field for lithography techniques is expected to expand,development of a novel material for use in lithography will be desired.For example, as miniaturization of resist patterns progress, improvementwill be demanded for resist materials with respect to variouslithography properties such as resolution and the like.

Mask error factor (MEF) is one of such lithography properties. The MEFis a parameter that indicates how faithfully mask patterns of differingdimensions can be reproduced by using the same exposure dose with fixedpitch and changing the mask size (i.e., mask reproducibility). In theformation of a resist pattern using a conventional resist composition,when the mask size (e.g., the hole diameter of a hole pattern, or theline width of a line and space pattern) is changed, the amount of lightirradiated on exposed portions is changed. As a result, disadvantagesare likely to be caused in that the actual size of the formed pattern isdeviated from the mask size, and pattern collapse occurs in theformation of an extremely fine pattern with a narrow pitch. For example,when a hole pattern having a hole diameter of about no more than 100 nmis formed, the circularity of the holes is likely to be deteriorated.

In view of the above situation, the present inventors made diligentstudies. As a result, the present inventors have found that the aboveproblems could be solved by using a polymeric compound containing thestructural units (a0) and (a1) described later as a base component, andproposed a positive resist composition containing the polymeric compound(Japanese Patent Application No. 2008-247802). However, as a result offurther diligent studies of the present inventors, it was found that,although the positive resist composition exhibited excellent lithographyproperties, the heat resistance was unsatisfactory. Therefore, thelatitude of the bake temperature during resist pattern formation wassmall, and improvement in the heat resistance has been demanded in termsof process.

The present invention takes the above circumstances into consideration,with an object of providing a positive resist composition which exhibitsexcellent lithography properties and excellent heat resistance, and amethod of forming a resist pattern using the positive resistcomposition.

As a result of further studies of the present inventors, it has beenfound that the heat resistance of the aforementioned polymeric compoundcan be improved by adding a structural unit containing a specifichydroxy group-containing aliphatic hydrocarbon group in a specificamount. The present invention has been completed based on this finding.

Specifically, a first aspect of the present invention is a positiveresist composition including a base component (A) which exhibitsincreased solubility in an alkali developing solution under action ofacid and an acid-generator component (B) which generates acid uponexposure,

the base component (A) including a polymeric compound (A1) containing astructural unit (a0) represented by general formula (a0-1) shown below,a structural unit (a1) derived from an acrylate ester containing an aciddissociable, dissolution inhibiting group, and a structural unit (a3)derived from an acrylate ester containing a hydroxy group-containingaliphatic hydrocarbon group represented by general formula (a3-1) shownbelow, and

the amount of the structural unit (a3) based on the combined total ofall structural units constituting the polymeric compound (A1) being inthe range of 1 to 30 mol %.

In formula (a0-1), R represents a hydrogen atom, an alkyl group of 1 to5 carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; R²represents a divalent linking group; and R³ represents a cyclic groupcontaining —SO₂— group within the ring skeleton thereof. In formula(a3-1), R represents a hydrogen atom, an alkyl group of 1 to 5 carbonatoms or a halogenated alkyl group of 1 to 5 carbon atoms; each of Ra,Rb and Rc independently represents a hydrogen atom, an alkyl group of 1to 5 carbon atoms, a hydroxy group or a hydroxyalkyl group, providedthat at least one of Ra, Rb and Rc represents a hydroxy group or ahydroxyalkyl group; and Rd represents a single bond or a divalentlinking group.

A second aspect of the present invention is a method of forming a resistpattern, including applying a positive resist composition according tothe first aspect on a substrate to form a resist film, subjecting theresist film to exposure, and subjecting the resist film to alkalideveloping to form a resist pattern.

In the present description and claims, the term “aliphatic” is arelative concept used in relation to the term “aromatic”, and defines agroup or compound that has no aromaticity.

The term “alkyl group” includes linear, branched or cyclic, monovalentsaturated hydrocarbon, unless otherwise specified.

The term “alkylene group” includes linear, branched or cyclic divalentsaturated hydrocarbon, unless otherwise specified. The same applies forthe alkyl group within an alkoxy group.

A “halogenated alkyl group” is a group in which part or all of thehydrogen atoms of an alkyl group is substituted with a halogen atom.Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

A “fluorinated alkyl group” or a “fluorinated alkylene group” is a groupin which part or all of the hydrogen atoms of an alkyl group or analkylene group have been substituted with a fluorine atom.

The term “structural unit” refers to a monomer unit that contributes tothe formation of a polymeric compound (resin, polymer, copolymer).

A “structural unit derived from an acrylate ester” refers to astructural unit that is formed by the cleavage of the ethylenic doublebond of an acrylate ester.

The term “acrylate ester” is a generic term that includes acrylateesters having a hydrogen atom bonded to the carbon atom on theα-position, and acrylate esters having a substituent (an atom other thana hydrogen atom or a group) bonded to the carbon atom on the α-position.Examples of the substituent bonded to the carbon atom on the α-positioninclude an alkyl group of 1 to 5 carbon atoms, a halogenated alkyl groupof 1 to 5 carbon atoms and a hydroxyalkyl group.

A carbon atom on the α-position of an acrylate ester refers to thecarbon atom bonded to the carbonyl group, unless specified otherwise.

The term “exposure” is used as a general concept that includesirradiation with any form of radiation.

According to the present invention, there are provided a positive resistcomposition which exhibits excellent lithography properties andexcellent heat resistance, and a method of forming a resist patternusing the positive resist composition.

DETAILED DESCRIPTION OF THE INVENTION

<<Positive Resist Composition>>

The positive resist composition of the present invention (hereafter,frequently referred to simply as “resist composition”) includes a basecomponent (A) (hereafter, referred to as “component (A)”) which exhibitsincreased solubility in an alkali developing solution under action ofacid and an acid-generator component (B) (hereafter, referred to as“component (B)”) which generates acid upon exposure.

In the positive resist composition, when radial rays are irradiated(when exposure is conducted), acid is generated from the component (B),and the solubility of the component (A) in an alkali developing solutionis increased by the action of the generated acid. Therefore, in theformation of a resist pattern, by conducting selective exposure of aresist film formed by using the positive resist composition of thepresent invention, the solubility of the exposed portions in an alkalideveloping solution is increased, whereas the solubility of theunexposed portions in an alkali developing solution is unchanged, andhence, a resist pattern can be formed by alkali developing.

Here, the term “base component” refers to an organic compound capable offorming a film. As the base component, an organic compound having amolecular weight of 500 or more can be preferably used. When the organiccompound has a molecular weight of 500 or more, the film-forming abilityis improved, and a resist pattern of nano level can be easily formed.

The “organic compound having a molecular weight of 500 or more” whichcan be used as a base component is broadly classified into non-polymersand polymers.

In general, as a non-polymer, any of those which have a molecular weightin the range of 500 to less than 4,000 is used. Hereafter, a non-polymerhaving a molecular weight in the range of 500 to less than 4,000 isreferred to as a low molecular weight compound.

As a polymer, any of those which have a molecular weight of 2,000 ormore is used. Hereafter, a polymer having a molecular weight of 2,000 ormore is referred to as a polymeric compound. With respect to a polymericcompound, the “molecular weight” is the weight average molecular weightin terms of the polystyrene equivalent value determined by gelpermeation chromatography (GPC). Hereafter, a polymeric compound isfrequently referred to simply as a “resin”.

<Component (A)>

[Polymeric Compound (A1)]

The polymeric compound (A1) (hereafter, referred to as “component (A1)”)includes a structural unit (a0) represented by general formula (a0-1), astructural unit (a1) derived from an acrylate ester containing an aciddissociable, dissolution inhibiting group, and a structural unit (a3)derived from an acrylate ester containing a hydroxy group-containingaliphatic hydrocarbon group represented by general formula (a3-1).

The component (A1) preferably includes a structural unit (a2) derivedfrom an acrylate ester containing a lactone-containing cyclic group, aswell as the structural units (a0), (a1)) and (a3).

(Structural Unit (a0))

In general formula (a0-1), R represents a hydrogen atom, an alkyl groupof 1 to 5 carbon atoms or a halogenated alkyl group of 1 to 5 carbonatoms.

As the alkyl group for R, a linear or branched alkyl group ispreferable, and specific examples include a methyl group, an ethylgroup, a propyl group, an isopropyl group, an n-butyl group, an isobutylgroup, a tert-butyl group, a pentyl group, an isopentyl group and aneopentyl group.

Examples of the halogenated alkyl group for R include groups in whichpart or all of the hydrogen atoms within the aforementioned alkyl groupshas been substituted with a halogen atom. Examples of the halogen atomwithin the halogenated alkyl group include a fluorine atom, a chlorineatom, a bromine atom and an iodine atom, and a fluorine atom isparticularly desirable.

As R, a hydrogen atom, an alkyl group of 1 to 5 carbon atoms or afluorinated alkyl group of 1 to 5 carbon atoms is preferable, and ahydrogen atom or a methyl group is particularly desirable in terms ofindustrial availability.

In general formula (a0-1), R² represents a divalent linking group.

Preferable examples of R² include a divalent hydrocarbon group which mayhave a substituent, and a divalent linking group containing a heteroatom.

With respect to the “divalent hydrocarbon group which may have asubstituent” for R², the hydrocarbon group “has a substituent” meansthat part or all of the hydrogen atoms within the hydrocarbon group hasbeen substituted with a group or an atom other than a hydrogen atom.

The hydrocarbon group may be either an aliphatic hydrocarbon group or anaromatic hydrocarbon group. An “aliphatic hydrocarbon group” refers to ahydrocarbon group that has no aromaticity.

The aliphatic hydrocarbon group may be saturated or unsaturated. Ingeneral, the aliphatic hydrocarbon group is preferably saturated.

As specific examples of the aliphatic hydrocarbon group, a linear orbranched aliphatic hydrocarbon group, and an aliphatic hydrocarbon groupcontaining a ring in the structure thereof can be given.

The linear or branched aliphatic hydrocarbon group preferably has 1 to10 carbon atoms, more preferably 1 to 8, still more preferably 1 to 5,and most preferably 1 or 2.

As the linear aliphatic hydrocarbon group, a linear alkylene group ispreferable. Specific examples thereof include a methylene group [—CH₂—],an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], atetramethylene group [—(CH₂)₄—] and a pentamethylene group [—(CH₂)₅—].

As the branched aliphatic hydrocarbon group, branched alkylene groupsare preferred, and specific examples include various alkylalkylenegroups, including alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—;alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—,—C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylenegroups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; andalkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and—CH₂CH(CH₃)CH₂CH₂—. As the alkyl group within the alkylalkylene group, alinear alkyl group of 1 to 5 carbon atoms is preferable.

The linear or branched aliphatic hydrocarbon group (chain-like aliphatichydrocarbon group) may or may not have a substituent. Examples ofsubstituents include a fluorine atom, a fluorinated alkyl group of 1 to5 carbon atoms, and an oxygen atom (═O).

As examples of the hydrocarbon group containing a ring in the structurethereof, a cyclic aliphatic hydrocarbon group (a group in which twohydrogen atoms have been removed from an aliphatic hydrocarbon ring),and a group in which the cyclic aliphatic hydrocarbon group is bonded tothe terminal of the aforementioned chain-like aliphatic hydrocarbongroup or interposed within the aforementioned chain-like aliphatichydrocarbon group, can be given.

The cyclic aliphatic hydrocarbon group preferably has 3 to 20 carbonatoms, and more preferably 3 to 12 carbon atoms.

The cyclic aliphatic hydrocarbon group may be either a polycyclic groupor a monocyclic group. As the monocyclic group, a group in which twohydrogen atoms have been removed from a monocycloalkane of 3 to 6 carbonatoms is preferable. Examples of the monocycloalkane includecyclopentane and cyclohexane.

As the polycyclic group, a group in which two hydrogen atoms have beenremoved from a polycycloalkane of 7 to 12 carbon atoms is preferable.Examples of the polycycloalkane include adamantane, norbornane,isobornane, tricyclodecane and tetracyclododecane.

The cyclic aliphatic hydrocarbon group may or may not have asubstituent. Examples of the substituent include an alkyl group of 1 to5 carbon atoms, a fluorine atom, a fluorinated alkyl group of 1 to 5carbon atoms, and an oxygen atom (═O).

Examples of aromatic hydrocarbon groups include a divalent aromatichydrocarbon group in which one hydrogen atom has been removed from abenzene ring of a monovalent aromatic hydrocarbon group such as a phenylgroup, a biphenyl group, a fluorenyl group, a naphthyl group, an anthrylgroup or a phenanthryl group;

an aromatic hydrocarbon group in which part of the carbon atomsconstituting the ring of the aforementioned divalent aromatichydrocarbon group has been substituted with a hetero atom such as anoxygen atom, a sulfur atom or a nitrogen atom; and

and an aromatic hydrocarbon group in which one hydrogen atom has beenremoved from a benzene ring of an arylalkyl group such as a benzylgroup, a phenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethylgroup, a 1-naphthylethyl group or a 2-naphthylethyl group.

The aromatic hydrocarbon group may or may not have a substituent.Examples of the substituent include an alkyl group of 1 to 5 carbonatoms, a fluorine atom, a fluorinated alkyl group of 1 to 5 carbonatoms, and an oxygen atom (═O).

With respect to the “divalent linking group containing a hetero atom”for R², a hetero atom within the “divalent linking group containing ahetero atom” refers to an atom other than carbon and hydrogen, andexamples thereof include an oxygen atom, a nitrogen atom, a sulfur atomand a halogen atom.

Specific examples of the divalent linking group containing a hetero atominclude plar groups such as —O—, —C(═O)—, —C(═O)—O—, a carbonate bond(—O—C(═O)—O—), —S—, —S(═O)₂—, —S(═O)₂—O—, —NH—, —NR⁰⁴— (R⁰⁴ represents asubstituent such as an alkyl group or an acyl group), —NH—C(═O)— and═N—. Further, a combination of at least one of these polar groups with adivalent hydrocarbon group can also be used. As examples of the divalenthydrocarbon group, the same groups as those described above for thehydrocarbon group which may have a substituent can be given, and alinear or branched aliphatic hydrocarbon group is preferable.

R² may or may not have an acid dissociable portion in the structurethereof.

An “acid dissociable portion” refers to a portion within the organicgroup which is dissociated from the organic group by action of acidgenerated upon exposure. When the R² group has an acid dissociableportion, it preferably has an acid dissociable portion having a tertiarycarbon atom.

In the present invention, as the divalent linking group for R², analkylene group, a divalent aliphatic cyclic group or a divalent linkinggroup containing a hetero atom is preferable. Among these, an alkylenegroup or a divalent linking group containing a hetero atom isparticularly desirable.

When R² represents an alkylene group, it preferably has 1 to 10 carbonatoms, more preferably 1 to 6, still more preferably 1 to 4, and mostpreferably 1 to 3. Specific examples of alkylene groups include theaforementioned linear alkylene groups and branched alkylene groups.

When R² represents a divalent aliphatic cyclic group, as the aliphaticcyclic group, the same aliphatic cyclic groups as those described abovefor the “aliphatic hydrocarbon group containing a ring in the structurethereof” can be used.

As the aliphatic cyclic group, a group in which two hydrogen atoms havebeen removed from cyclopentane, cyclohexane, norbornane, isobornane,adamantane, tricyclodecane or tetracyclododecane is particularlydesirable.

When R² represents a divalent linking group containing a hetero atom,preferable examples of the divalent linking group containing a heteroatom include —O—, —C(═O)—O—, —C(═O)—, —NH—C(═O)—, —NH—, —NR⁰⁴— (R⁰⁴represents a substituent such as an alkyl group or an acyl group), —S—,—S(═O)₂—, —S(═O)₂—O—, a group represented by the formula -A-O—B—, and agroup represented by the formula -[A-C(═O)—O]_(d)—B—. Herein, each of Aand B independently represents a divalent hydrocarbon group which mayhave a substituent, and d represents an integer of 0 to 3.

When R² represents NR⁰⁴—, R⁰⁴ represents a substituent such as an alkylgroup or an acyl group. The substituent (an alkyl group, an acyl groupor the like) preferably has 1 to 10 carbon atoms, more preferably 1 to8, and most preferably 1 to 5.

In the group represented by the formula -A-O—B— or -[A-C(═O)—O]_(d)—B—,each of A and B independently represents a divalent hydrocarbon groupwhich may have a substituent.

Examples of divalent hydrocarbon groups for A and B which may have asubstituent include the same groups as those described above for the“divalent hydrocarbon group which may have a substituent” usable as R².

As A, a linear aliphatic hydrocarbon group is preferable, morepreferably a linear alkylene group, still more preferably a linearalkylene group of 1 to 5 carbon atoms, and a methylene group or anethylene group is particularly desirable.

As B, a linear or branched aliphatic hydrocarbon group is preferable,and a methylene group, an ethylene group or an alkylmethylene group ismore preferable. The alkyl group within the alkylmethylene group ispreferably a linear alkyl group of 1 to 5 carbon atoms, more preferablya linear alkyl group of 1 to 3 carbon atoms, and most preferably amethyl group.

In the group represented by the formula [A-C(═O)—O]_(d)—B—, d representsan integer of 0 to 3, preferably an integer of 0 to 2, more preferably 0or 1, and most preferably 1.

In general formula (a0-1), R³ represents a cyclic group containing —SO₂—within the ring skeleton thereof. More specifically, R³ is a cyclicgroup in which the sulfur atom (S) within the —SO₂— group forms part ofthe ring skeleton thereof.

The cyclic group for R³ refers to a cyclic group including a ring thatcontains —SO₂— within the ring skeleton thereof, and this ring iscounted as the first ring. A cyclic group in which the only ringstructure is the ring that contains —SO₂— in the ring skeleton thereofis referred to as a monocyclic group, and a group containing other ringstructures is described as a polycyclic group regardless of thestructure of the other rings. The cyclic group for R³ may be either amonocyclic group or a polycyclic group.

As R³, a cyclic group containing —O—SO₂— within the ring skeletonthereof, i.e., a cyclic group containing a sultone ring in which —O—S—within the —O—SO₂— group forms part of the ring skeleton thereof isparticularly desirable.

The cyclic group for R³ preferably has 3 to 30 carbon atoms, morepreferably 4 to 20, still more preferably 4 to 15, and most preferably 4to 12.

Herein, the number of carbon atoms refers to the number of carbon atomsconstituting the ring skeleton, excluding the number of carbon atomswithin a substituent.

The cyclic group for R³ may be either an aliphatic cyclic group or anaromatic cyclic group.

An aliphatic cyclic group is preferable.

Examples of aliphatic cyclic groups for R³ include the aforementionedcyclic aliphatic hydrocarbon groups in which part of the carbon atomsconstituting the ring skeleton thereof has been substituted with —SO₂—or —O—SO₂—.

More specifically, examples of monocyclic groups include amonocycloalkane in which one hydrogen atom have been removed therefromand a —CH₂— group constituting the ring skeleton thereof has beensubstituted with —SO₂—; and a monocycloalkane in which one hydrogen atomhave been removed therefrom and a —CH₂—CH₂— group constituting the ringskeleton thereof has been substituted with —O—SO₂—. Examples ofpolycyclic groups include a polycycloalkane (a bicycloalkane, atricycloalkane, a tetracycloalkane or the like) in which one hydrogenatom have been removed therefrom and a —CH₂— group constituting the ringskeleton thereof has been substituted with —SO₂—; and a polycycloalkanein which one hydrogen atom have been removed therefrom and a —CH₂—CH₂—group constituting the ring skeleton thereof has been substituted with—O—SO₂—.

The cyclic group for R³ may have a substituent. Examples of thesubstituent include an alkyl group, an alkoxy group, a halogen atom, ahalogenated alkyl group, a hydroxy group, an oxygen atom (═O), —COOR″,—OC(═O)R″, a hydroxyalkyl group and a cyano group. R″ represents ahydrogen atom or an alkyl group.

The alkyl group for the substituent is preferably an alkyl group of 1 to6 carbon atoms. Further, the alkyl group is preferably a linear alkylgroup or a branched alkyl group. Specific examples include a methylgroup, an ethyl group, a propyl group, an isopropyl group, an n-butylgroup, an isobutyl group, a tert-butyl group, a pentyl group, anisopentyl group, a neopentyl group and a hexyl group. Among these, amethyl group or ethyl group is preferable, and a methyl group isparticularly desirable.

As the alkoxy group for the substituent, an alkoxy group of 1 to 6carbon atoms is preferable. Further, the alkoxy group is preferably alinear alkoxy group or a branched alkyl group. Specific examples of thealkoxy group include the aforementioned alkyl groups for the substituenthaving an oxygen atom (—O—) bonded thereto.

Examples of the halogen atom for the substituent include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom is preferable.

Examples of the halogenated alkyl group for the substituent includegroups in which part or all of the hydrogen atoms within theaforementioned alkyl groups has been substituted with the aforementionedhalogen atoms.

As examples of the halogenated lower alkyl group for the substituent,groups in which part or all of the hydrogen atoms of the aforementionedalkyl groups for the substituent have been substituted with theaforementioned halogen atoms can be given. As the halogenated alkylgroup, a fluorinated alkyl group is preferable, and a perfluoroalkylgroup is particularly desirable.

In the —COOR″ group and the —OC(═O)R″ group, R″ preferably represents ahydrogen atom or a linear, branched or cyclic alkyl group of 1 to 15carbon atoms.

When R″ represents a linear or branched alkyl group, it is preferably analkyl group of 1 to 10 carbon atoms, more preferably an alkyl group of 1to 5 carbon atoms, and most preferably a methyl group or an ethyl group.

When R″ is a cyclic alkyl group (cycloalkyl group), it preferably has 3to 15 carbon atoms, more preferably 4 to 12 carbon atoms, and mostpreferably 5 to 10 carbon atoms. As examples of the cycloalkyl group,groups in which one or more hydrogen atoms have been removed from amonocycloalkane or a polycycloalkane such as a bicycloalkane,tricycloalkane or tetracycloalkane, which may or may not be substitutedwith a fluorine atom or a fluorinated alkyl group, may be used. Specificexamples include groups in which one or more hydrogen atoms have beenremoved from a monocycloalkane such as cyclopentane and cyclohexane; andgroups in which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane.

The hydroxyalkyl group for the substituent preferably has 1 to 6 carbonatoms, and specific examples thereof include the aforementioned alkylgroups for the substituent in which at least one hydrogen atom has beensubstituted with a hydroxy group.

More specific examples of R³ include groups represented by generalformulas (3-1) to (3-4) shown below.

In the formulas, A′ represents an oxygen atom, a sulfur atom, or analkylene group of 1 to 5 carbon atoms which may contain an oxygen atomor a sulfur atom; z represents an integer of 0 to 2; and R⁶ representsan alkyl group, an alkoxy group, a halogenated alkyl group, a hydroxylgroup, —COOR″, —OC(═O)R″, a hydroxyalkyl group or a cyano group, whereinR″ represents a hydrogen atom or an alkyl group.

In general formulas (3-1) to (3-4) above, A′ represents an oxygen atom(—O—), a sulfur atom (—S—), or an alkylene group of 1 to 5 carbon atomswhich may contain an oxygen atom or a sulfur atom.

As the alkylene group of 1 to 5 carbon atoms represented by A′, a linearor branched alkylene group is preferable, and examples thereof include amethylene group, an ethylene group, an n-propylene group and anisopropylene group.

Examples of alkylene groups that contain an oxygen atom or a sulfur atominclude the aforementioned alkylene groups in which —O— or —S— is bondedto the terminal of the alkylene group or interposed within the alkylgroup. Specific examples of such alkylene groups include —O—CH₂—,—CH₂—O—CH₂—, —CH₂—S—CH₂—.

As A′, an alkylene group of 1 to 5 carbon atoms, —O— or —S— ispreferable. As the alkylene group of 1 to 5 carbon atoms, a methylenegroup is particularly desirable.

z represents an integer of 0 to 2, and is most preferably 0.

When z is 2, the plurality of R² may be the same or different from eachother.

As the alkyl group, alkoxy group, halogenated alkyl group, —COOR″,—OC(═O)R″ and hydroxyalkyl group for R⁶, the same alkyl groups, alkoxygroups, halogenated alkyl groups, —COOR″, —OC(═O)R″ and hydroxyalkylgroups as those described above as the substituent which the cyclicgroup for R³ may have can be used.

Specific examples of the cyclic groups represented by general formulas(3-1) to (3-4) are shown below. In the formulas shown below, “Ac”represents an acetyl group.

Among the examples shown above, as R³, a group represented by generalformula (3-1), (3-3) or (3-4) shown below is preferable, and a cyclicgroup represented by general formula (3-1) shown below is particularlydesirable.

More specifically, as R³, it is preferable to use at least one cyclicgroup selected from the group consisting of groups represented bychemical formulas (3-1-1), (3-1-18), (3-3-1) and (3-4-1) above, and agroup represented by chemical formula (3-1-1) above is particularlydesirable.

In the present invention, as the structural unit (a0), a structural unitrepresented by general formula (a0-1-11) shown below is particularlydesirable.

In the formula, R is the same as defined above; R⁰² represents a linearor branched alkylene group or −A-C(═O)—O—B— (wherein A and B are thesame as defined above); and A′ is the same as defined above.

The linear or branched alkylene group for R⁰² preferably has 1 to 10carbon atoms, more preferably 1 to 8, still more preferably 1 to 5,still more preferably 1 to 3, and most preferably 1 or 2.

A and B in the formula -A-C(═O)—O—B— are respectively the same asdefined for A and B in the formula -[A-C(═O)—O]^(d)—B— described abovein the explanation of R₂.

A′ is preferably a methylene group, an oxygen atom (—O—) or a sulfuratom (—S—).

As the structural unit (a0), one type of structural unit may be usedalone, or two or more types of structural units may be used incombination.

In the component (A1), the amount of the structural unit (a0) based onthe combined total of all structural units constituting the component(A1) is preferably 1 to 60 mol %, more preferably 5 to 50 mol %, stillmore preferably 10 to 40 mol %, and most preferably 15 to 40 mol %. Whenthe amount of the structural unit (a0) is at least as large as the lowerlimit of the above-mentioned range, a resist pattern formed using thepositive resist composition including the component (A1) exhibitsexcellent properties with respect to mask error factor (MEF), shape ofthe resist pattern (e.g., rectangularity of a line pattern, circularityof a hole pattern), in-plane uniformity (CDU), line width roughness(LWR), and the like.

Further, when the amount of the structural unit (a0) is no more than theupper limit of the above-mentioned range, excellent properties can beobtained with respect to heat resistance and resolution.

(Structural Unit (a1))

The structural unit (a1) is a structural unit derived from an acrylateester containing an acid dissociable, dissolution inhibiting group.

The acid dissociable, dissolution inhibiting group within the structuralunit (a1) has an alkali dissolution inhibiting effect that renders theentire component (A1) insoluble in an alkali developing solution priorto dissociation, and then following dissociation under action of acidgenerated from the component (B) upon exposure, increases the solubilityof the entire component (A1) in the alkali developing solution.

As the acid dissociable, dissolution inhibiting group, any of thosewhich have been proposed as acid dissociable, dissolution inhibitinggroups for a base resin of a chemically amplified resist may be used.Generally, groups that form either a cyclic or chain-like tertiary alkylester with the carboxyl group of the (meth)acrylic acid, and acetal-typeacid dissociable, dissolution inhibiting groups such as alkoxyalkylgroups are widely known. Here, the term “(meth)acrylate ester” is ageneric term that includes either or both of the acrylate ester having ahydrogen atom bonded to the α-position and the methacrylate ester havinga methyl group bonded to the α-position.

Here, a tertiary alkyl ester describes a structure in which an ester isformed by substituting the hydrogen atom of a carboxyl group with achain-like or cyclic tertiary alkyl group, and a tertiary carbon atomwithin the chain-like or cyclic tertiary alkyl group is bonded to theoxygen atom at the terminal of the carbonyloxy group (—C(O)—O—). In thistertiary alkyl ester, the action of acid causes cleavage of the bondbetween the oxygen atom and the tertiary carbon atom.

The chain-like or cyclic alkyl group may have a substituent.

Hereafter, for the sake of simplicity, groups that exhibit aciddissociability as a result of the formation of a tertiary alkyl esterwith a carboxyl group are referred to as “tertiary alkyl ester-type aciddissociable, dissolution inhibiting groups”.

Examples of tertiary alkyl ester-type acid dissociable, dissolutioninhibiting groups include aliphatic branched, acid dissociable,dissolution inhibiting groups and aliphatic cyclic group-containing aciddissociable, dissolution inhibiting groups.

The term “aliphatic branched” refers to a branched structure having noaromaticity. The “aliphatic branched, acid dissociable, dissolutioninhibiting group” is not limited to be constituted of only carbon atomsand hydrogen atoms (not limited to hydrocarbon groups), but ispreferably a hydrocarbon group. Further, the “hydrocarbon group” may beeither saturated or unsaturated, but is preferably saturated.

As an example of the aliphatic branched, acid dissociable, dissolutioninhibiting group, for example, a group represented by the formula—C(R⁷¹)(R⁷²)(R⁷³) can be given (in the formula, each of R⁷¹ to R⁷³independently represents a linear alkyl group of 1 to 5 carbon atoms).The group represented by the formula —C(R⁷¹)(R⁷²)(R⁷³) preferably has 4to 8 carbon atoms, and specific examples include a tert-butyl group, a2-methyl-2-butyl group, a 2-methyl-2-pentyl group and a3-methyl-3-pentyl group. Among these, a tert-butyl group is particularlydesirable.

The term “aliphatic cyclic group” refers to a monocyclic group orpolycyclic group that has no aromaticity.

The “aliphatic cyclic group” within the structural unit (a1) may or maynot have a substituent. Examples of the substituent include an alkylgroup of 1 to 5 carbon atoms, an alkoxy group of 1 to 5 carbon atoms, afluorine atom, a fluorinated alkyl group of 1 to 5 carbon atoms, and anoxygen atom (═O).

The basic ring of the “aliphatic cyclic group” exclusive of substituentsis not limited to be constituted from only carbon and hydrogen (notlimited to hydrocarbon groups), but is preferably a hydrocarbon group.Further, the “hydrocarbon group” may be either saturated or unsaturated,but is preferably saturated. Furthermore, the “aliphatic cyclic group”is preferably a polycyclic group.

As such aliphatic cyclic groups, groups in which one or more hydrogenatoms have been removed from a monocycloalkane or a polycycloalkane suchas a bicycloalkane, tricycloalkane or tetracycloalkane which may or maynot be substituted with a lower alkyl group, a fluorine atom or afluorinated alkyl group, may be used. Specific examples include groupsin which one or more hydrogen atoms have been removed from amonocycloalkane such as cyclopentane or cyclohexane; and groups in whichone or more hydrogen atoms have been removed from a polycycloalkane suchas adamantane, norbornane, isobornane, tricyclodecane ortetracyclododecane. Further, these groups in which one or more hydrogenatoms have been removed from a monocycloalkane and groups in which oneor more hydrogen atoms have been removed from a polycycloalkane may havepart of the carbon atoms constituting the ring replaced with an etherealoxygen atom (—O—).

Examples of aliphatic cyclic group-containing acid dissociable,dissolution inhibiting groups include

(i) a group which has a tertiary carbon atom on the ring structure of amonovalent aliphatic cyclic group; and

(ii) a group which has a branched alkylene group containing a tertiarycarbon atom, and a monovalent aliphatic cyclic group to which thetertiary carbon atom is bonded.

Specific examples of (i) a group which has a tertiary carbon atom on thering structure of a monovalent aliphatic cyclic group include groupsrepresented by general formulas (1-1) to (1-9) shown below.

Specific examples of (ii) a group which has a branched alkylene groupcontaining a tertiary carbon atom, and a monovalent aliphatic cyclicgroup to which the tertiary carbon atom is bonded include groupsrepresented by general formulas (2-1) to (2-6) shown below.

In the formulas above, R¹⁴ represents an alkyl group; and g representsan integer of 0 to 8.

In the formulas above, each of R¹⁵ and R¹⁶ independently represents analkyl group.

As the alkyl group for R¹⁴, a linear or branched alkyl group ispreferable.

The linear alkyl group preferably has 1 to 5 carbon atoms, morepreferably 1 to 4, and still more preferably 1 or 2. Specific examplesinclude a methyl group, an ethyl group, an n-propyl group, an n-butylgroup and an n-pentyl group. Among these, a methyl group, an ethyl groupor an n-butyl group is preferable, and a methyl group or an ethyl groupis more preferable.

The branched alkyl group preferably has 3 to 10 carbon atoms, and morepreferably 3 to 5. Specific examples of such branched alkyl groupsinclude an isopropyl group, an isobutyl group, a tert-butyl group, anisopentyl group and a neopentyl group, and an isopropyl group isparticularly desirable.

g is preferably an integer of 0 to 3, more preferably 1 to 3, and stillmore preferably 1 or 2.

As the alkyl group for R¹⁵ and R¹⁶, the same alkyl groups as those forR¹⁴ can be used.

In formulas (1-1) to (1-9) and (2-1) to (2-6), part of the carbon atomsconstituting the ring may be replaced with an ethereal oxygen atom(—O—).

Further, in formulas (1-1) to (1-9) and (2-1) to (2-6), one or more ofthe hydrogen atoms bonded to the carbon atoms constituting the ring maybe substituted with a substituent. Examples of the substituent includean alkyl group of 1 to 5 carbon atoms, a fluorine atom and a fluorinatedalkyl group.

An “acetal-type acid dissociable, dissolution inhibiting group”generally substitutes a hydrogen atom at the terminal of analkali-soluble group such as a carboxy group or hydroxyl group, so as tobe bonded with an oxygen atom. When acid is generated upon exposure, thegenerated acid acts to break the bond between the acetal-type aciddissociable, dissolution inhibiting group and the oxygen atom to whichthe acetal-type, acid dissociable, dissolution inhibiting group isbonded.

Examples of acetal-type acid dissociable, dissolution inhibiting groupsinclude groups represented by general formula (p1) shown below.

In the formula, R¹′ and R²′ each independently represent a hydrogen atomor an alkyl group of 1 to 5 carbon atoms; n represents an integer of 0to 3; and Y represents an alkyl group of 1 to 5 carbon atoms or analiphatic cyclic group.

In general formula (p1) above, n is preferably an integer of 0 to 2,more preferably 0 or 1, and most preferably 0.

As the alkyl group of 1 to 5 carbon atoms for R¹′ and R²′, the samealkyl groups of 1 to 5 carbon atoms as those described above for R canbe used, although a methyl group or ethyl group is preferable, and amethyl group is particularly desirable.

In the present invention, it is preferable that at least one of R¹′ andR²′ be a hydrogen atom. That is, it is preferable that the aciddissociable, dissolution inhibiting group (p1) is a group represented bygeneral formula (p1-1) shown below.

In the formula, R¹′, n and Y are the same as defined above.

As the alkyl group for Y, the same alkyl groups as those described abovefor R can be used.

As the aliphatic cyclic group for Y, any of the aliphaticmonocyclic/polycyclic groups which have been proposed for conventionalArF resists and the like can be appropriately selected for use. Forexample, the same groups described above in connection with the“aliphatic cyclic group” can be used.

Further, as the acetal-type, acid dissociable, dissolution inhibitinggroup, groups represented by general formula (p2) shown below can alsobe used.

In the formula, R¹⁷ and R¹⁸ each independently represent a linear orbranched alkyl group or a hydrogen atom; and R¹⁹ represents a linear,branched or cyclic alkyl group; or R¹⁷ and R¹⁹ each independentlyrepresents a linear or branched alkylene group, and the terminal of R¹⁷is bonded to the terminal of R¹⁹ to form a ring.

The alkyl group for R¹⁷ and R¹⁸ preferably has 1 to 15 carbon atoms, andmay be either linear or branched. As the alkyl group, an ethyl group ora methyl group is preferable, and a methyl group is most preferable.

It is particularly desirable that either one of R¹⁷ and R¹⁸ be ahydrogen atom, and the other be a methyl group.

R¹⁹ represents a linear, branched or cyclic alkyl group which preferablyhas 1 to 15 carbon atoms, and may be any of linear, branched or cyclic.

When R¹⁹ represents a linear or branched alkyl group, it is preferablyan alkyl group of 1 to 5 carbon atoms, more preferably an ethyl group ormethyl group, and most preferably an ethyl group.

When R¹⁹ represents a cycloalkyl group, it preferably has 4 to 15 carbonatoms, more preferably 4 to 12 carbon atoms, and most preferably 5 to 10carbon atoms. As examples of the cycloalkyl group, groups in which oneor more hydrogen atoms have been removed from a monocycloalkane or apolycycloalkane such as a bicycloalkane, tricycloalkane ortetracycloalkane, which may or may not be substituted with a fluorineatom or a fluorinated alkyl group, may be used. Specific examplesinclude groups in which one or more hydrogen atoms have been removedfrom a monocycloalkane such as cyclopentane and cyclohexane; and groupsin which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane. Among these, a group in which oneor more hydrogen atoms have been removed from adamantane is preferable.

In general formula (p2) above, R¹⁷ and R¹⁹ may each independentlyrepresent a linear or branched alkylene group (preferably an alkylenegroup of 1 to 5 carbon atoms), and the terminal of R¹⁹ may be bonded tothe terminal of R¹⁷.

In such a case, a cyclic group is formed by R¹⁷, R¹⁹, the oxygen atomhaving R¹⁹ bonded thereto, and the carbon atom having the oxygen atomand R¹⁷ bonded thereto. Such a cyclic group is preferably a 4- to7-membered ring, and more preferably a 4- to 6-membered ring. Specificexamples of the cyclic group include tetrahydropyranyl group andtetrahydrofuranyl group.

Specific examples of acetal-type acid dissociable; dissolutioninhibiting groups include groups represented by formulas (p3-1) to(p3-12) shown below.

In the formulas above, R¹³ represents a hydrogen atom or a methyl group;and g is the same as defined above.

Specific examples of the structural unit (a1)) include a structural unitrepresented by general formula (a1-0-1) shown below and a structuralunit represented by general formula (a1-0-2) shown below.

In the formulas, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; X¹represents an acid dissociable, dissolution inhibiting group; Y²represents a divalent linking group; and X² represents an aciddissociable, dissolution inhibiting group.

In general formula (a1-0-1), R is the same as defined for R in generalformula (a0-1).

X¹ is not particularly limited as long as it is an acid dissociable,dissolution inhibiting group. Examples thereof include theaforementioned tertiary alkyl ester-type acid dissociable, dissolutioninhibiting groups and acetal-type acid dissociable, dissolutioninhibiting groups, and tertiary alkyl ester-type acid dissociable,dissolution inhibiting groups are preferable.

In general formula (a1-0-2), R is the same as defined above.

X² is the same as defined for X¹ in general formula (a1-0-1).

As examples of the divalent linking group for Y², the same groups asthose described above for R² in formula (a0-1) can be given.

As Y², the aforementioned alkylene group, a divalent aliphatic cyclicgroup or a divalent linking group containing a hetero atom ispreferable. Among these, a divalent linking group containing a heteroatom is preferable, and a linear group containing an oxygen atom as aheteratom, e.g., a group containing an ester bond is particularlydesirable.

More specifically, a group represented by the aforementioned formula-A-O—B— or -A-C(═O)—O—B— is preferable, and a group represented by theformula —(CH₂)_(x)—C(═O)—O—(CH₂)_(y)— is particularly desirable.

x represents an integer of 1 to 5, preferably 1 or 2, and mostpreferably 1.

y represents an integer of 1 to 5, preferably 1 or 2, and mostpreferably 1.

Specific examples of the structural unit (a1) include structural unitsrepresented by general formulas (a1-1) to (a1-4) shown below.

In the formulas, X′ represents a tertiary alkyl ester-type aciddissociable, dissolution inhibiting group; Y represents an alkyl groupof 1 to 5 carbon atoms or an aliphatic cyclic group; n represents aninteger of 0 to 3; Y² represents a divalent linking group; R is the sameas defined above; and each of R¹′ and R²′ independently represents ahydrogen atom or an alkyl group of 1 to 5 carbon atoms.

Examples of the tertiary alkyl ester-type acid dissociable, dissolutioninhibiting group for X′ include the same tertiary alkyl ester-type aciddissociable, dissolution inhibiting groups as those described above forX¹.

As R¹′, R²′, n and Y are respectively the same as defined for R¹′, R²′,n and Y in general formula (p1) described above in connection with the“acetal-type acid dissociable, dissolution inhibiting group”.

As examples of Y², the same groups as those described above for Y² ingeneral formula (a1-0-2) can be given.

Specific examples of structural units represented by general formula(a1-1) to (a1-4) are shown below.

In the formulas shown below, R^(α) represents a hydrogen atom, a methylgroup or a trifluoromethyl group.

As the structural unit (a1), one type of structural unit may be used, ortwo or more types may be used in combination.

In the present invention, in terms of achieving excellent lithographyproperties with respect to resolution, the shape of resist pattern andthe like, it is particularly desirable that the structural unit (a1)includes at least one structural unit selected from the group consistingof a structural unit represented by general formula (a1-0-11) shownbelow, a structural unit represented by general formula (a1-0-12) shownbelow and a structural unit represented by general formula (a1-0-2)shown below.

In the formulas, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; R²¹represents an alkyl group; R²² represents a group which forms analiphatic monocyclic group with the carbon atom to which R²² is bonded;R²³ represents a branched alkyl group; R²⁴ represents a group whichforms an aliphatic polycyclic group with the carbon atom to which R²⁴ isbonded; Y² represents a divalent linking group; and X² represents anacid dissociable, dissolution inhibiting group.

In the formulas, R, Y² and X² are the same as defined above.

In general formula (a1-0-11), as the alkyl group for R²¹, the same alkylgroups as those described above for R¹⁴ in formulas (1-1) to (1-9) canbe used, preferably a methyl group or an ethyl group, and mostpreferably an ethyl group.

As the aliphatic monocyclic group formed by R²² and the carbon atoms towhich R²² is bonded, the same aliphatic cyclic groups as those describedabove for the aforementioned tertiary alkyl ester-type acid dissociable,dissolution inhibiting group and which are monocyclic can be used.Specific examples include groups in which one or more hydrogen atomshave been removed from a monocycloalkane. The monocycloalkane ispreferably a 3- to 11-membered ring, more preferably a 3- to 8-memberedring, still more preferably a 4- to 6-membered ring, and most preferablya 5- or 6-membered ring.

The monocycloalkane may or may not have part of the carbon atomsconstituting the ring replaced with an ethereal oxygen atom (—O—).

Further, the monocycloalkane may have a substituent such as an alkylgroup of 1 to 5 carbon atoms, a fluorine atom or a fluorinated alkylgroup.

As an examples of R²² constituting such an aliphatic cyclic group, analkylene group which may have an ethereal oxygen atom (—O—) interposedbetween the carbon atoms can be given.

Specific examples of structural units represented by general formula(a1-0-11) include structural units represented by the aforementionedformulas (a1-1-16) to (a1-1-23). Among these, a structural unitrepresented by general formula (a1-1-02) shown below which includes thestructural units represented by the aforementioned formulas (a1-1-16),(a1-1-17) and (a1-1-20) to (a1-1-23) is preferable. Further, astructural unit represented by general formula (a1-1-02′) shown below isalso preferable.

In the formulas shown below, h is preferably 1 or 2, and most preferably2.

In the formulas, R and R²¹ are the same as defined above; and hrepresents an integer of 1 to 3.

In general formula (a1-0-12), as the branched alkyl group for R²³, thesame alkyl groups as those described above for R¹⁴ which are branchedcan be used, and an isopropyl group is particularly desirable.

As the aliphatic polycyclic group formed by R²⁴ and the carbon atoms towhich R²⁴ is bonded, the same aliphatic cyclic groups as those describedabove for the aforementioned tertiary alkyl ester-type acid dissociable,dissolution inhibiting group and which are polycyclic can be used.

Specific examples of structural units represented by general formula(a1-0-12) include structural units represented by the aforementionedformulas (a1-1-26) to (a1-1-31).

Examples of structural units represented by general formula (a1-0-2)include structural units represented by the aforementioned formulas(a1-3) and (a1-4).

As a structural unit represented by general formula, (a1-0-2), those inwhich Y² is a group represented by the aforementioned formula -A-O—B— or-A-C(═O)—O—B— is particularly desirable.

Preferable examples of such structural units include a structural unitrepresented by general formula (a1-3-01) shown below, a structural unitrepresented by general formula (a1-3-02) shown below, and a structuralunit represented by general formula (a1-3-03) shown below.

In the formula, R and R¹⁴ are the same as defined above; R¹² representsa hydrogen atom or a methyl group; and a represents an integer of 1 to10.

In the formula, R and R¹⁴ are the same as defined above; R¹² representsa hydrogen atom or a methyl group; a represents an integer of 1 to 10;and n′ represents an integer of 0 to 3.

In the formula, R is as defined above; each of Y²′ and Y²″ independentlyrepresents a divalent linking group; X′ represents an acid dissociable,dissolution inhibiting group; and n represents an integer of 1 to 3.

In general formulas (a1-3-01) and (a1-3-02), R¹² is preferably ahydrogen atom.

a is preferably an integer of 1 to 8, more preferably 1 to 5, and mostpreferably 1 or 2.

n′ is preferably 1 or 2, and most preferably 2.

Specific examples of structural units represented by general formula(a1-3-01) include structural units represented by the aforementionedformulas (a1-3-25) and (a 1-3-26).

Specific examples of structural units represented by general formula(a1-3-02) include structural units represented by the aforementionedformulas (a1-3-27) and (a 1-3-28).

In general formula (a1-3-03), as the divalent linking group for Y²′ andY²″, the same groups as those described above for Y² in general formula(a1-3) can be used.

As Y²′, a divalent hydrocarbon group which may have a substituent ispreferable, a linear aliphatic hydrocarbon group is more preferable, anda linear alkylene group is still more preferable. Among linear alkylenegroups, a linear alkylene group of 1 to 5 carbon atoms is preferable,and a methylene group or an ethylene group is particularly desirable.

As Y²″, a divalent hydrocarbon group which may have a substituent ispreferable, a linear aliphatic hydrocarbon group is more preferable, anda linear alkylene group is still more preferable. Among linear alkylenegroups, a linear alkylene group of 1 to 5 carbon atoms is preferable,and a methylene group or an ethylene group is particularly desirable.

As the acid dissociable, dissolution inhibiting group for X′, the samegroups as those described above can be used. X′ is preferably a tertiaryalkyl ester-type acid dissociable, dissolution inhibiting group, morepreferably the aforementioned group (i) which has a tertiary carbon atomon the ring structure of a monovalent aliphatic cyclic group. Among theaforementioned groups (i), a group represented by general formula (1-1)above is preferable.

n represents an integer of 0 to 3, preferably an integer of 0 to 2, morepreferably 0 or 1, and most preferably 1.

As the structural unit represented by general formula (a1-3-03), astructural unit represented by general formula (a1-3-03-1) shown belowwhich encompasses structural units represented by the aforementionedformula (a1-3-29) or (a1-3-31), or a structural unit represented bygeneral formula (a1-3-03-2) shown below which encompasses structuralunits represented by the aforementioned formula (a1-3-30) or (a1-3-32)is particularly desirable. Among these, a structural unit represented bythe formula (a1-3-03-1) is preferable.

In the formulas, R and R¹⁴ are the same as defined above; a representsan integer of 1 to 10; b represents an integer of 1 to 10; and trepresents an integer of 0 to 3.

a is preferably an integer of 1 to 5, and most preferably 1 or 2.

b is preferably an integer of 1 to 5, and most preferably 1 or 2.

t is preferably an integer of 1 to 3, and most preferably 1 or 2.

In the component (A1), as the structural unit (a1), one type ofstructural unit may be used alone, or two or more types of structuralunits may be used in combination.

In the present invention, it is particularly desirable to include atleast two types of structural units as the structural unit (a1). As aresult, the lithography properties can be further improved. Thestructural unit (a1) within the component (A1) preferably includes 2 to4 types of structural units, more preferably 2 or 3 types of structuralunits.

When the structural unit (a1) includes at least two types of structuralunits, it is preferable that at least one of the at least two structuralunits is a structural unit selected from the group consisting of astructural unit represented by general formula (a1-0-11), a structuralunit represented by general formula (a1-0-12) and a structural unitrepresented by general formula (a1-0-2).

The structural unit (a1) including at least two types of structuralunits may consist of structural units selected from the group consistingof a structural unit represented by general formula (a1-0-11), astructural unit represented by general formula (a1-0-12) and astructural unit represented by general formula (a1-0-2). Alternatively,the structural unit (a1) may be a combination of at least one structuralunit selected from the aforementioned group and a structural unit whichdoes not fall under the category of the aforementioned group.

As examples of the structural unit which can be used in combination withat least one structural unit selected from the group consisting of astructural unit represented by general formula (a1-0-11), a structuralunit represented by general formula (a1-0-12) and a structural unitrepresented by general formula (a1-0-2) and does not fall under thecategory of the aforementioned group, a structural unit represented bygeneral formula (a1-1-01) shown below which includes the structuralunits represented by the aforementioned (a1-1-1), (a1-1-2), (a1-1-7) to(a1-1-15) described above as specific examples of structural unitsrepresented by general formula (a1-1), structural units represented bygeneral formula (a1-2) and structural units represented by generalformula (a1-4) can be given.

As a structural unit represented by general formula (a1-1-01), astructural unit represented by general formula (a1-1-101) shown belowwhich includes the aforementioned formulas (a1-1-1) and (a1-1-2) isparticularly desirable.

In the formulas, R is the same as defined above; each of R²⁵ and R¹¹independently represents a linear alkyl group of 1 to 5 carbon atoms;and R²⁴ is the same as defined above.

In the component (A1), the amount of the structural unit (a1) based onthe combined total of all structural units constituting the component(A1) is preferably 10 to 80 mol %, more preferably 20 to 70 mol %, andstill more preferably 25 to 60 mol %. When the amount of the structuralunit (a1) is at least as large as the lower limit of the above-mentionedrange, a pattern can be easily formed using a resist compositionprepared from the component (A1). On the other hand, when the amount ofthe structural unit (a1) is no more than the upper limit of theabove-mentioned range, a good balance can be achieved with the otherstructural units.

(Structural Unit (a3))

The structural unit (a3) is a structural unit derived from an acrylateester containing a hydroxy group-containing aliphatic hydrocarbon groupand is represented by the aforementioned general formula (a3-1).

In formula (a3-1), R is the same as defined for R in the aforementionedformula (a0-1).

Each of Ra, Rb and Rc independently represents a hydrogen atom, an alkylgroup of 1 to 5 carbon atoms, a hydroxyl group or a hydroxyalkyl group.

As the alkyl group for Ra, Rb and Rc, the same alkyl groups as thosedescribed above for R can be used.

The hydroxyalkyl group is a group in which part or all of the hydrogenatoms within an alkyl group have been substituted with a hydroxyl group.The alkyl group within the hydroxyalkyl group is the same as defined forthe alkyl group represented by R. It is particularly desirable that thehydroxyalkyl group has one hydroxyl group.

At least one of Ra, Rb and Rc represents a hydroxyl group or ahydroxyalkyl group.

In the present invention, it is preferable that one or two of Ra, Rb andRc represent a hydroxyl group or a hydroxyalkyl group, and the remainingtwo or one of Ra, Rb and Rc represent a hydrogen atom. Further, it isparticularly desirable that one or two of Ra, Rb and Rc represent ahydroxyl group, and the remaining two or one of Ra, Rb and Rc representa hydrogen atom.

Rd represents a single bond or a divalent linking group. As examples ofthe divalent linking group for Rd, the same divalent linking groups asthose described above for R² in the aforementioned formula (a0-1) can begiven.

As Rd, an alkylene group, an ester bond (—C(═O)—O—) or a combination ofthese is preferable. As the alkylene group within the divalent linkinggroup for Rd, a linear or branched alkylene group is preferable.Specific examples include the same linear alkylene groups and branchedalkylene groups as those described above for the aliphatic hydrocarbongroup represented by R².

As Rd, a single bond or -Rd′-C(═O)—O— (in the formula, Rd′ represents alinear or branched alkylene group) is particularly desirable.

The linear or branched alkylene group for Rd′ preferably has 1 to 10carbon atoms, more preferably 1 to 8 carbon atoms, still more preferably1 to 5 carbon atoms, still more preferably 1 to 3 carbon atoms, and mostpreferably 1 or 2 carbon atoms.

As the linear alkylene group for Rd′, a methylene group or an ethylenegroup is preferable, and a methylene group is particularly desirable. Asthe branched alkylene group for Rd′, an alkylmethylene group or analkylethylene group is preferable, and —CH(CH₃)—, —C(CH₃)₂— or—C(CH₃)₂CH₂— is particularly desirable.

As the structural unit (a3), one type of structural unit may be used, ortwo or more types may be used in combination.

In the component (A1), the amount of the structural unit (a3) based onthe combined total of all structural units constituting the component(A1) is in the range of 1 to 30 mol %, preferably 5 to 30 mol %, andstill more preferably 5 to 25 mol %. When the amount of the structuralunit (a3) is at least as large as the lower limit of the above-mentionedrange, a satisfactory improvement in the heat resistance can beachieved. Further, the hydrophilicity of the component (A) is improved,and hence, the compatibility of the component (A) with the developingsolution is improved. As a result, the alkali solubility of the exposedportions improves, which contributes to favorable improvements in theresolution. On the other hand, when the amount of the structural unit(a3) is no more than the upper limit of the above-mentioned range, agood balance can be achieved with the other structural units, andexcellent lithography properties can be achieved. In addition, diffusionof acid generated from the component (B) can be suppressed, andexcellent properties can be achieved with respect to mask error factorand resist pattern shape.

(Structural Unit (a2))

The structural unit (a2) is a structural unit derived from an acrylateester containing a lactone-containing cyclic group.

The term “lactone-containing cyclic group” refers to a cyclic groupincluding one ring containing a —O—C(O)— structure (lactone ring). Theterm “lactone ring” refers to a single ring containing a —O—C(O)—structure, and this ring is counted as the first ring. Alactone-containing cyclic group in which the only ring structure is thelactone ring is referred to as a monocyclic group, and groups containingother ring structures are described as polycyclic groups regardless ofthe structure of the other rings.

When the component (A1) is used for forming a resist film, thelactone-containing cyclic group of the structural unit (a2) is effectivein improving the adhesion between the resist film and the substrate, andincreasing the compatibility with the developing solution containingwater.

As the structural unit (a2), there is no particular limitation, and anarbitrary structural unit may be used.

Specific examples of lactone-containing monocyclic groups include agroup in which one hydrogen atom has been removed from a 4- to6-membered lactone ring, such as a group in which one hydrogen atom hasbeen removed from β-propionolatone, a group in which one hydrogen atomhas been removed from γ-butyrolactone, and a group in which one hydrogenatom has been removed from δ-valerolactone. Further, specific examplesof lactone-containing polycyclic groups include groups in which onehydrogen atom has been removed from a lactone ring-containingbicycloalkane, tricycloalkane or tetracycloalkane.

More specifically, examples of the structural unit (a2) includestructural units represented by general formulas (a2-1) to (a2-5) shownbelow.

In the formulas, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; eachR′ independently represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms, an alkoxy group of 1 to 5 carbon atoms or —COOR″, whereinR″ represents a hydrogen atom or an alkyl group; R²⁹ represents a singlebond or a divalent linking group; s″ represents an integer of 0 to 2; A″represents an oxygen atom, a sulfur atom or an alkylene group of 1 to 5carbon atoms which may contain an oxygen atom or a sulfur atom; and mrepresents 0 or 1.

In general formulas (a2-1) to (a2-5), R is the same as defined for R inthe structural unit (a1).

Examples of the alkyl group of 1 to 5 carbon atoms for R′ include amethyl group, an ethyl group, a propyl group, an n-butyl group and atert-butyl group.

Examples of the alkoxy group of 1 to 5 carbon atoms for R′ include amethoxy group, an ethoxy group, an n-propoxy group, an iso-propoxygroup, an n-butoxy group and a tert-butoxy group

In terms of industrial availability, R′ is preferably a hydrogen atom.

The alkyl group for R″ may be any of linear, branched or cyclic.

When R″ is a linear or branched alkyl group, it preferably has 1 to 10carbon atoms, more preferably 1 to 5 carbon atoms.

When R″ is a cyclic alkyl group (cycloalkyl group), it preferably has 3to 15 carbon atoms, more preferably 4 to 12 carbon atoms, and mostpreferably 5 to 10 carbon atoms. As examples of the cycloalkyl group,groups in which one or more hydrogen atoms have been removed from amonocycloalkane or a polycycloalkane such as a bicycloalkane,tricycloalkane or tetracycloalkane, which may or may not be substitutedwith a fluorine atom or a fluorinated alkyl group, may be used. Examplesof such groups include groups in which one or more hydrogen atoms havebeen removed from a monocycloalkane such as cyclopentane or cyclohexane;and groups in which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane.

As examples of A″, the same groups as those described above for A′ ingeneral formula (3-1) can be given. A″ is preferably an alkylene groupof 1 to 5 carbon atoms, an oxygen atom (—O—) or a sulfur atom (—S—), andmore preferably an alkylene group of 1 to 5 carbon atoms or —O—. As thealkylene group of 1 to 5 carbon atoms, a methylene group or adimethylethylene group is preferable, and a methylene group isparticularly desirable.

R²⁹ represents a single bond or a divalent linking group. As examples ofthe divalent linking group, the same divalent linking groups as thosedescribed above for R² in the aforementioned formula (a0-1) can begiven. Among these, an alkylene group, an ester bond (—C(═O)—O—) or acombination of these is preferable. The alkylene group as a divalentlinking group for R²⁹ is preferably a linear or branched alkylene group.Specific examples include the same linear alkylene groups and branchedalkylene groups as those described above for the aliphatic hydrocarbongroup represented by R².

As R²⁹, a single bond or —R²⁹′—C(═O)—O— (in the formula, R²⁹′ representsa linear or branched alkylene group) is particularly desirable.

The linear or branched alkylene group for R²⁹′ preferably has 1 to 10carbon atoms, more preferably 1 to 8, still more preferably 1 to 5,still more preferably 1 to 3, and most preferably 1 or 2.

As the linear alkylene group for R²⁹′, a methylene group or an ethylenegroup is preferable, and a methylene group is particularly desirable. Asthe branched alkylene group for R²⁹′, an alkylmethylene group or analkylethylene group is preferable, and —CH(CH₃)—, —C(CH₃)₂— or—C(CH₃)₂CH₂— is particularly desirable.

In formula (a2-1), s″ is preferably 1 or 2.

Specific examples of structural units represented by general formulas(a2-1) to (a2-5) are shown below. In the formulas shown below, R^(α)represents a hydrogen atom, a methyl group or a trifluoromethyl group.

In the component (A1), as the structural unit (a2), one type ofstructural unit may be used, or two or more types may be used incombination.

In the present invention, as the structural unit (a2) within thecomponent (A1), it is preferable to include at least one structural unitselected from the group consisting of structural units represented bythe aforementioned general formulas (a2-1) to (a2-5), more preferably atleast one structural unit selected from the group consisting ofstructural units represented by the aforementioned general formulas(a2-1) to (a2-3), and most preferably at least one structural unitselected from the group consisting of structural units represented bythe aforementioned general formulas (a2-1) and (a2-2).

In terms of improving the adhesion between a substrate and a resist filmformed using a positive resist composition containing the component (A1)and increasing the compatibility with a developing solution, the amountof the structural unit (a2) within the component (A1), based on thecombined total of all structural units constituting the component (A1))is preferably 1 to 50 mol %, more preferably 5 to 50 mol %, and stillmore preferably 10 to 45 mol %. By ensuring the above-mentioned range,MEF, CDU and the pattern shape can be further improved.

Further, in terms of achieving excellent lithography properties, thetotal amount of the structural unit (a0) and the structural unit (a2)(the amount of the structural unit (a0) when the component (A1) containsno structural unit (a2)) within the component (A1), based on thecombined total of all structural units constituting the component (A1)is preferably 1 to 70 mol %, more preferably 5 to 70 mol %, still morepreferably 10 to 65 mol %, and most preferably 20 to 65 mol %. Byensuring the above-mentioned range, MEF, CDU and the pattern shape canbe further improved.

When the component (A1) contains both of the structural unit (a0) andthe structural unit (a2), the amount of the structural unit (a0) withinthe component (A1), based on the combined total of all structural unitsconstituting the component (A1) is preferably 1 to 40 mol %, morepreferably 10 to 35 mol %, and most preferably 15 to 30 mol %; and theamount of the structural unit (a2) within the component (A1), based onthe combined total of all structural units constituting the component(A1) is preferably 1 to 45 mol %, more preferably 10 to 45 mol %, andmost preferably 20 to 45 mol %.

(Other Structural Units)

The component (A1) may also have a structural unit other than theabove-mentioned structural units (a1) to (a3), as long as the effects ofthe present invention are not impaired.

As such a structural unit, any other structural unit which cannot beclassified as one of the above structural units (a1) to (a3) can be usedwithout any particular limitation, and any of the multitude ofconventional structural units used within resist resins for ArF excimerlasers or KrF excimer lasers (and particularly for ArF excimer lasers)can be used.

Examples of such a structural unit include the structural units (a4) and(a3′) shown below.

The structural unit (a4) is a structural unit derived from an acrylateester containing a non-acid dissociable, aliphatic polycyclic group.

As the aliphatic polycyclic group for the structural unit (a4), any ofthe multitude of conventional polycyclic groups used within the resincomponent of resist compositions for ArF excimer lasers or KrF excimerlasers (and particularly for ArF excimer lasers) can be used. Specificexamples include groups in which one or more hydrogen atoms have beenremoved from a polycycloalkane such as a bicycloalkane, tricycloalkaneor tetracycloalkane.

As the aliphatic polycyclic group, at least one polycyclic groupselected from amongst a tricyclodecyl group, adamantyl group,tetracyclododecyl group, isobornyl group, and norbornyl group isparticularly desirable in consideration of industrial availability andthe like.

These aliphatic polycyclic groups may have a linear or branched alkylgroup of 1 to 5 carbon atoms as a substituent.

Specific examples of the structural unit (a4) include units withstructures represented by general formulas (a4-1) to (a4-5) shown below.

In the formulas, R is the same as defined above.

When the structural unit (a4) is included in the component (A1), theamount of the structural unit (a4) based on the combined total of allthe structural units that constitute the component (A1)) is preferablywithin the range from 1 to 30 mol %, and more preferably from 10 to 20mol %.

The structural unit (a3′) is a structural unit derived from an acrylateester containing a polar group-containing aliphatic hydrocarbon groupand does not fall under the category of the aforementioned structuralunit (a3).

Examples of the polar group include a hydroxyl group, cyano group,carboxyl group, or hydroxyalkyl group in which some of the hydrogenatoms of the alkyl group have been substituted with fluorine atoms,although a hydroxyl group is particularly desirable.

Examples of the aliphatic hydrocarbon group include linear or branchedhydrocarbon groups (preferably alkylene groups) of 1 to 10 carbon atoms,and polycyclic aliphatic hydrocarbon groups (polycyclic groups). Thesepolycyclic groups can be selected appropriately from the multitude ofgroups that have been proposed for the resins of resist compositionsdesigned for use with ArF excimer lasers. The polycyclic grouppreferably has 7 to 30 carbon atoms.

Of the various possibilities, structural units derived from an acrylateester that include a polycyclic group that contains a hydroxyl group,cyano group, carboxyl group or a hydroxyalkyl group in which part of thehydrogen atoms of the alkyl group have been substituted with fluorineatoms are particularly desirable. Examples of the polycyclic groupinclude groups in which two or more hydrogen atoms have been removedfrom a bicycloalkane, tricycloalkane, tetracycloalkane or the like.Specific examples include groups in which two or more hydrogen atomshave been removed from a polycycloalkane such as adamantane, norbornane,isobornane, tricyclodecane or tetracyclododecane. Of these polycyclicgroups, groups in which two or more hydrogen atoms have been removedfrom norbornane or tetracyclododecane are preferred industrially.

When the aliphatic hydrocarbon group within the polar group-containingaliphatic hydrocarbon group is a linear or branched hydrocarbon group of1 to 10 carbon atoms, the structural unit (a3′) is preferably astructural unit derived from a hydroxyethyl ester of acrylic acid.

On the other hand, when the hydrocarbon group is a polycyclic group,structural units represented by general formulas (a3′-2) and (a3′-3)shown below are preferable.

In the formulas, R is the same as defined above; k′ is an integer of 1to 3; t′ is an integer of 1 to 3; l′ is an integer of 1 to 5; and s′ isan integer of 1 to 3.

In formula (a3′-2), k′ is preferably 1. The cyano group is preferablybonded to the 5th or 6th position of the norbornyl group.

In formula (a3′-3), t′ is preferably 1. l′ is preferably 1.

s′ is preferably 1.

In formula (a3′-3), the oxygen atom (—O—) bonded to the carbonyl groupis preferably bonded to the 2nd or 3rd position of the norbornane ring.Further, the fluorinated alcohol group (—(CH₂)—C(C_(s)F_(2s+1))₂OH) ispreferably bonded to the 5th or 6th position of the norbornyl group.

As the structural unit (a3′), one type of structural unit may be used,or two or more types may be used in combination.

The component (A1) is a copolymer including the structural units (a0),(a1) and (a3).

Examples of such a copolymer include a copolymer consisting of thestructural units (a0), (a1) and (a3), and a copolymer consisting ofstructural units (a0), (a1), (a2) and (a3).

In the present invention, it is particularly desirable that such acopolymer contains, as the structural unit (a1), at least one memberselected from the group consisting of a structural unit represented bygeneral formula (a1-0-11), a structural unit represented by generalformula (a1-0-12), and a structural unit represented by general formula(a1-1-01).

Further, as described above, such a copolymer preferably contains atleast two types of structural units as the structural unit (a1). It ismore preferable that at least one of the at least two structural unitsis selected from the group consisting of a structural unit representedby general formula (a1-0-11) and a structural unit represented bygeneral formula (a1-0-12). It is particularly desirable that both of theat least two types of structural units are selected from theaforementioned group.

In the present invention, as the component (A1), a copolymer includingsix types of structural units shown in general formula (A1-10) below, acopolymer including five types of structural units shown in any one ofgeneral formulas (A1-11) to (A1-14) below, a copolymer including fourtypes of structural units shown in any one of general formulas (A1-15)to (A1-18) below, or a copolymer including three types of structuralunits shown in general formula (A1-19) or (A1-20) below is preferable.

In the formula, R, R²⁹, R⁰², A′, R²³, R²¹, h, a, b, R¹⁴ and Rd are thesame as defined above; i represents 0 or 1; and the plurality of R maybe the same or different from each other.

In the formulas, R, R²⁹, R⁰², A′, R²³, R²¹, h, Rd, i, a, b and R¹⁴ arethe same as defined above, and the plurality of R may be the same ordifferent from each other.

In the formulas, R, R²⁹, A″, R⁰², A′, R²³, R²¹, h, Rd, i, a, b, R¹⁴ andR¹¹ are the same as defined above, and the plurality of R may be thesame or different from each other.

In the formulas, R, R²⁹, R⁰², A′, R²³, Rd, i, R²¹ and h are the same asdefined above, and the plurality of R may be the same or different fromeach other.

In the formulas, R, R⁰², A′, R²³, a, b, R¹⁴, Rd, i and R¹¹ are the sameas defined above, and the plurality of R may be the same or differentfrom each other.

In the formulas, R, R⁰², A′, R²¹, h, Rd, i, a, b and R¹⁴ are the same asdefined above, and the plurality of R may be the same or different fromeach other.

The weight average molecular weight (Mw) (the polystyrene equivalentvalue determined by gel permeation chromatography) of the component(A 1) is not particularly limited, but is preferably 2,000 to 50,000,more preferably 3,000 to 30,000, and most preferably 5,000 to 20,000.When the weight average molecular weight is no more than the upper limitof the above-mentioned range, the resist composition exhibits asatisfactory solubility in a resist solvent. On the other hand, when theweight average molecular weight is at least as large as the lower limitof the above-mentioned range, dry etching resistance and thecross-sectional shape of the resist pattern becomes satisfactory.

Further, the dispersity (Mw/Mn) is preferably 1.0 to 5.0, morepreferably 1.0 to 3.0, and most preferably 1.2 to 2.5. Here, Mn is thenumber average molecular weight.

In the component (A), as the component (A1), one type may be used, ortwo or more types of compounds may be used in combination.

In the component (A), the amount of the component (A1) based on thetotal weight of the component (A) is preferably 25% by weight or more,more preferably 50% by weight or more, still more preferably 75% byweight or more, and may be even 100% by weight. When the amount of thecomponent (A1) is 25% by weight or more, various lithography propertiesare improved.

The component (A1) can be obtained, for example, by a conventionalradical polymerization or the like of the monomers corresponding witheach of the structural units, using a radical polymerization initiatorsuch as azobisisobutyronitrile (AIBN).

Furthermore, in the component (A1), by using a chain transfer agent suchas HS—CH₂—CH₂—CH₂—C(CF₃)₂—OH, a —C(CF₃)₂—OH group can be introduced atthe terminals of the component (A1). Such a copolymer having introduceda hydroxyalkyl group in which some of the hydrogen atoms of the alkylgroup are substituted with fluorine atoms is effective in reducingdeveloping defects and LER (line edge roughness: unevenness of the sidewalls of a line pattern).

As the monomers for deriving the corresponding structural units,commercially available monomers may be used, or the monomers may besynthesized by a conventional method.

For example, as a monomer for deriving the structural unit (a0), acompound represented by general formula (a0-1-0) shown below (hereafter,referred to as “compound (a0-1-0)”) can be used.

In the formula, R, R² and R³ are the same as defined above.

The method for producing the compound (a0-1-0) is not particularlylimited, and the compound (a0-1-0) can be produced by a conventionalmethod.

For example, in the presence of a base, a compound (X-2) represented bygeneral formula (X-2) shown below is added to a solution obtained bydissolving a compound (X-1) represented by general formula (X-1) shownbelow in a reaction solvent, and a reaction is effected to therebyobtain a compound (a0-1-0).

Examples of the base include inorganic bases such as sodium hydride,K₂CO₃ and Cs₂CO₃; and organic bases such as triethylamine,4-dimethylaminopyridine (DMAP) and pyridine. Examples of condensingagents include carbodiimide reagents such asethyldiisopropylaminocarbodiimide hydrochloride (EDCI),dicyclohexylcarboxylmide (DCC), diisopropylcarbodiimide andcarbodiimidazole; tetraethyl pyrophosphate; andbenzotriazole-N-hydroxytrisdimethylaminophosphonium hexafluorophosphide(Bop reagent).

If desired, an acid may be used. As the acid, any acid generally usedfor dehydration/condensation may be used. Specific examples includeinorganic acids such as hydrochloric acid, sulfuric acid and phosphoricacid; and organic acids such as methanesulfonic acid,trifluoromethanesulfonic acid, benzenesulfonic acid andp-toluenesulfonic acid. These acids can be used individually, or in acombination of two or more.

In the formula, R, R² and R³ are the same as defined above.

In the resist composition of the present invention, the component (A)may contain “a base component which exhibits increased solubility in analkali developing solution under action of acid” other than thecomponent (A1) (hereafter, referred to as “component (A2)”).

The component (A2) is not particularly limited, and any of the multitudeof conventional base components used within chemically amplified resistcompositions (e.g., base resins used within chemically amplified resistcompositions for ArF excimer lasers or KrF excimer lasers, preferablyArF excimer lasers) can be used. For example, as a base resin for ArFexcimer laser, a base resin having the aforementioned structural unit(a1)) as an essential component, and optionally the aforementionedstructural units (a2) to (a5) can be used. Further, the component (A2)may contain a non-polymer (low molecular weight compound) having amolecular weight of 500 to less than 4,000.

As the component (A2), one type of resin may be used, or two or moretypes of resins may be used in combination.

In the resist composition of the present invention, the amount of thecomponent (A) can be appropriately adjusted depending on the thicknessof the resist film to be formed, and the like.

<Component (B)>

As the component (B), there is no particular limitation, and any of theknown acid generators used in conventional chemically amplified resistcompositions can be used. Examples of these acid generators arenumerous, and include onium salt acid generators such as iodonium saltsand sulfonium salts; oxime sulfonate acid generators; diazomethane acidgenerators such as bisalkyl or bisaryl sulfonyl diazomethanes andpoly(bis-sulfonyl)diazomethanes; nitrobenzylsulfonate acid generators;iminosulfonate acid generators; and disulfone acid generators.

As an onium salt acid generator, a compound represented by generalformula (b-1) or (b-2) shown below can be used.

In the formulas above, R¹″ to R³″, R⁵″ and R⁶″ each independentlyrepresent an aryl group or alkyl group which may have a substituent,wherein two of R¹″ to R³″ may be bonded to each other to form a ringwith the sulfur atom; and R⁴″ represents an alkyl group, a halogenatedalkyl group, an aryl group or an alkenyl group which may have asubstituent, with the provision that at least one of R¹″ to R³″represents an aryl group, and at least one of R⁵″ and R⁶″ represents anaryl group.

In formula (b-1), R¹″ to R³″ each independently represents an aryl groupwhich may have a substituent or an alkyl group which may have asubstituent. In formula (b-1), two of R¹″ to R³″ may be bonded to eachother to form a ring with the sulfur atom.

Further, among R¹″ to R³″, at least one group represents an aryl group.Among R¹″ to R³″, two or more groups are preferably aryl groups, and itis particularly desirable that all of R¹″ to R³″ are aryl groups.

The aryl group of R¹″ to R³″ is not particularly limited, and includes,for example, an aryl group of 6 to 20 carbon atoms. The aryl group ispreferably an aryl group having 6 to 10 carbon atoms because it can besynthesized at a low cost. Specific examples thereof include a phenylgroup and a naphthyl group.

The aryl group may have a substituent. The expression “has asubstituent” means that part or all of the hydrogen atoms within thearyl group has been substituted with a substituent. Examples of thesubstituent include an alkyl group, an alkoxy group, a halogen atom, ahydroxyl group, an alkoxyalkyloxy group, —O—R⁵⁰—CO—O—R⁵¹ (in theformula, R⁵⁰ represents an alkylene group, and R⁵¹ represents an aciddissociable group).

The alkyl group, with which hydrogen atoms of the aryl group may besubstituted, is preferably an alkyl group having 1 to 5 carbon atoms,and most preferably a methyl group, an ethyl group, a propyl group, ann-butyl group, or a tert-butyl group.

The alkoxy group, with which hydrogen atoms of the aryl group may besubstituted, is preferably an alkoxy group having 1 to 5 carbon atoms,more preferably a methoxy group, an ethoxy group, an n-propoxy group, aniso-propoxy group, an n-butoxy group or a tert-butoxy group, and mostpreferably a methoxy group or an ethoxy group.

The halogen atom, with which hydrogen atoms of the aryl group may besubstituted, is preferably a fluorine atom.

Examples of the alkoxyalkyloxy group which substitutes the hydrogenatoms within the aryl group include-O—C(R⁴⁷)(R⁴⁸)—O—R⁴⁹ (in the formula,each of R⁴⁷ and R⁴⁸ independently represents a hydrogen atom or a linearor branched alkyl group, and R⁴⁹ represents an alkyl group, wherein R⁴⁸and R⁴⁹ may be mutually bonded to form a ring structure, provided thatat least one of R⁴⁷ and R⁴⁸ represents a hydrogen atom).

The alkyl group for R⁴⁷ and R⁴⁸ preferably has 1 to 5 carbon atoms. Asthe alkyl group, an ethyl group or a methyl group is preferable, and amethyl group is most preferable.

Further, it is preferable that at least one of R⁴⁷ and R⁴⁸ represent ahydrogen atom, and the other represent a hydrogen atom or a methylgroup. It is particularly desirable that both of R⁴⁷ and R⁴⁸ represent ahydrogen atom.

The alkyl group for R⁴⁹ preferably has 1 to 15 carbon atoms, and may belinear, branched or cyclic.

The linear or branched alkyl group for R⁴⁹ preferably has 1 to 5 carbonatoms. Examples thereof include a methyl group, an ethyl group, a propylgroup, an n-butyl group and a tert-butyl group.

The cyclic alkyl group for R⁴⁹ preferably has 4 to 15 carbon atoms, morepreferably 4 to 12, and most preferably 5 to 10.

Specific examples thereof include groups in which one or more hydrogenatoms have been removed from a monocycloalkane or a polycycloalkane suchas a bicycloalkane, tricycloalkane or tetracycloalkane, and which may ormay not be substituted with an alkyl group of 1 to 5 carbon atoms, afluorine atom or a fluorinated alkyl group. Examples of themonocycloalkane include cyclopentane and cyclohexane. Examples ofpolycycloalkanes include adamantane, norbornane, isobornane,tricyclodecane and tetracyclododecane. Among these, a group in which oneor more hydrogen atoms have been removed from adamantane is preferable.

R⁴⁸ and R⁴⁹ may be mutually bonded to form a ring structure. In such acase, a cyclic group is formed by R⁴⁸, R⁴⁹, the oxygen atom having R⁴⁹bonded thereto, and the carbon atom having the oxygen atom and R⁴⁸bonded thereto. Such a cyclic group is preferably a 4- to 7-memberedring, and more preferably a 4- to 6-membered ring.

In the —O—R⁵⁰—CO—O—R⁵¹ group which may substitute the hydrogen atomswithin the aryl group, the alkylene group for R⁵⁰ is preferably a linearor branched alkylene group of 1 to 5 carbon atoms. Examples of thealkylene group include a methylene group, an ethylene group, atrimethylene group, a tetramethylene group and a 1,1-dimethylethylenegroup.

The acid dissociable group for R⁵¹ is not particularly limited as longas it is an organic group that is dissociable by the action of an acid(generated from the component (B) upon exposure), and examples thereofinclude the same acid dissociable, dissolution inhibiting groups asthose described above for the aforementioned structural unit (a1).However, unlike the aforementioned acid dissociable, dissolutioninhibiting group, the acid dissociable group is not necessarily requiredto exhibit the dissolution inhibiting effect in an alkali developingsolution.

Specific examples of the acid dissociable group include a tertiary alkylester-type acid dissociable group such as a cyclic or chain-liketertiary alkyl group; and an acetal-type acid dissociable group such asan alkoxyalkyl group. Among these, a tertiary alkyl ester-type aciddissociable group is preferable.

Specific examples of the tertiary alkyl ester-type acid dissociablegroup include a 2-methyl-2-adamantyl group, a 2-ethyl-2-adamantyl group,a 1-methyl-1-cyclopentyl group, a 1-ethyl-1-cyclopentyl group, a1-methyl-1-cyclohexyl group, a 1-ethyl-1-cyclohexyl group, a1-(1-adamantyl)-1-methylethyl group, a 1-(1-adamantyl)-1-methylpropylgroup, a 1-(1-adamantyl)-1-methylbutyl group, a1-(1-adamantyl)-1-methylpentyl group, a 1-(1-cyclopentyl)-1-methylethylgroup, a 1-(1-cyclopentyl)-1-methylpropyl group, a1-(1-cyclopentyl)-1-methylbutyl group, a1-(1-cyclopentyl)-1-methylpentyl group, a 1-(1-cyclohexyl)-1-methylethylgroup, a 1-(1-cyclohexyl)-1-methylpropyl group, a1-(1-cyclohexyl)-1-methylbutyl group, a 1-(1-cyclohexyl)-1-methylpentylgroup, a tert-butyl group, a tert-pentyl group and a tert-hexyl group.

The alkyl group for R¹″ to R³″ is not particularly limited and includes,for example, a linear, branched or cyclic alkyl group having 1 to 10carbon atoms. In terms of achieving excellent resolution, the alkylgroup preferably has 1 to 5 carbon atoms. Specific examples thereofinclude a methyl group, an ethyl group, an n-propyl group, an isopropylgroup, an n-butyl group, an isobutyl group, an n-pentyl group, acyclopentyl group, a hexyl group, a cyclohexyl group, a nonyl group, anda decyl group, and a methyl group is most preferable because it isexcellent in resolution and can be synthesized at a low cost.

The alkyl group may have a substituent. The expression “has asubstituent” means that part or all of the hydrogen atoms within thealkyl group has been substituted with a substituent. Examples of thesubstituent include the same groups as those described above for thesubstituent of the aforementioned aryl group.

When two of R¹″ to R³″ in formula (b-1) are bonded to each other to forma ring with the sulfur atom, it is preferable that the two of R¹″ to R³″form a 3 to 10-membered ring including the sulfur atom, and it isparticularly desirable that the two of R¹″ to R³″ form a 5 to 7-memberedring including the sulfur atom.

When two of R¹″ to R³″ in formula (b-1) are bonded to each other to forma ring with the sulfur atom, the remaining one of R¹″ to R³″ ispreferably an aryl group. As examples of the aryl group, the same as theabove-mentioned aryl groups for R¹″ to R³″ can be given.

As preferable examples of the cation moiety for the compound representedby general formula (b-1), those represented by formulas (I-1-1) to(I-1-13) shown below can be given. Among these, in terms of improvingthe lithography properties, a cation moiety having a triphenylmethaneskeleton, such as a cation moiety represented by any one of formulas(I-1-3), (I-1-5) to (I-1-7), (I-1-11) to (I-1-13) shown below isparticularly desirable.

In formulas (I-1-9) and (I-1-10), each of R⁹ and R¹⁰ independentlyrepresents a phenyl group or naphthyl group which may have asubstituent, an alkyl group of 1 to 5 carbon atoms, an alkoxy group or ahydroxy group.

u is an integer of 1 to 3, and most preferably 1 or 2.

R⁴″ represents an alkyl group, a halogenated alkyl group, an aryl groupor an alkenyl group which may have a substituent.

The alkyl group for R⁴″ may be any of linear, branched or cyclic.

The linear or branched alkyl group preferably has 1 to 10 carbon atoms,more preferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbonatoms.

The cyclic alkyl group preferably has 4 to 15 carbon atoms, morepreferably 4 to 10 carbon atoms, and most preferably 6 to 10 carbonatoms.

As an example of the halogenated alkyl group for R⁴″, a group in whichpart of or all of the hydrogen atoms of the aforementioned linear,branched or cyclic alkyl group have been substituted with halogen atomscan be given. Examples of the aforementioned halogen atom include afluorine atom, a chlorine atom, a bromine atom and an iodine atom, and afluorine atom is preferable.

In the halogenated alkyl group, the percentage of the number of halogenatoms based on the total number of halogen atoms and hydrogen atoms(halogenation ratio (%)) is preferably 10 to 100%, more preferably 50 to100%, and most preferably 100%. Higher halogenation ratio is preferablebecause the acid strength increases.

The aryl group for R⁴″ is preferably an aryl group of 6 to 20 carbonatoms.

The alkenyl group for R⁴″ is preferably an alkenyl group of 2 to 10carbon atoms.

With respect to R⁴″, the expression “may have a substituent” means thatpart of or all of the hydrogen atoms within the aforementioned linear,branched or cyclic alkyl group, halogenated alkyl group, aryl group oralkenyl group may be substituted with substituents (atoms other thanhydrogen atoms, or groups).

R⁴″ may have one substituent, or two or more substituents.

Examples of the substituent include a halogen atom, a hetero atom, analkyl group, and a group represented by the formula X-Q¹- (in theformula, Q¹ represents a divalent linking group containing an oxygenatom; and X represents a hydrocarbon group of 3 to 30 carbon atoms whichmay have a substituent).

Examples of halogen atoms and alkyl groups as substituents for R⁴″include the same halogen atoms and alkyl groups as those described abovewith respect to the halogenated alkyl group for R⁴″.

Examples of hetero atoms include an oxygen atom, a nitrogen atom, and asulfur atom.

In the group represented by formula X-Q¹-, Q¹ represents a divalentlinking group containing an oxygen atom.

Q¹ may contain an atom other than an oxygen atom. Examples of atomsother than an oxygen atom include a carbon atom, a hydrogen atom, asulfur atom and a nitrogen atom.

Examples of divalent linking groups containing an oxygen atom includenon-hydrocarbon, oxygen atom-containing linking groups such as an oxygenatom (an ether bond; —O—), an ester bond (—C(═O)—O—), an amido bond(—C(═O)—NH—), a carbonyl group (—C(═O)—) and a carbonate group(—O—C(═O)—O—); and combinations of the aforementioned non-hydrocarbon,hetero atom-containing linking groups with an alkylene group.

Specific examples of the combinations of the aforementionednon-hydrocarbon, hetero atom-containing linking groups and an alkylenegroup include —R⁹¹—O—, —R⁹²—O—C(═O)—, —C(═O)—O—R⁹³— and—C(═O)—O—R⁹³—O—C(═O)— (in the formulas, each of R⁹¹ to R⁹³ independentlyrepresents an alkylene group).

The alkylene group for R⁹¹ to R⁹³ is preferably a linear or branchedalkylene group, and preferably has 1 to 12 carbon atoms, more preferably1 to 5, and most preferably 1 to 3.

Specific examples of alkylene groups include a methylene group [—CH₂—];alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—, —C(CH₃)₂—,—C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)— and —C(CH₂CH₃)₂—; an ethylenegroup [—CH₂CH₂—]; alkylethylene groups such as —CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂— and —CH(CH₂CH₃)CH₂—; a trimethylene group(n-propylene group) [—CH₂CH₂CH₂—]; alkyltrimethylene groups such as—CH(CH₃)CH₂CH₂— and —CH₂CH(CH₃)CH₂—; a tetramethylene group[—CH₂CH₂CH₂CH₂—]; alkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—and —CH₂CH(CH₃)CH₂CH₂—; and a pentamethylene group [—CH₂CH₂CH₂CH₂CH₂—].

Q¹ is preferably a divalent linking group containing an ester linkage orether linkage, and more preferably a group of —R⁹¹—O—, —R⁹²—O—C(═O)—,—C(═O)—O—, —C(═O)—O—R⁹³—, or —C(═O)—O—R⁹³—O—C(═O)—.

In the group represented by the formula X-Q¹-, the hydrocarbon group forX may be either an aromatic hydrocarbon group or an aliphatichydrocarbon group.

The aromatic hydrocarbon group is a hydrocarbon group having an aromaticring. The aromatic hydrocarbon ring preferably has 3 to 30 carbon atoms,more preferably 5 to 30, still more preferably 5 to 20, still morepreferably 6 to 15, and most preferably 6 to 12. Here, the number ofcarbon atoms within a substituent(s) is not included in the number ofcarbon atoms of the aromatic hydrocarbon group.

Specific examples of aromatic hydrocarbon groups include an aryl groupwhich is an aromatic hydrocarbon ring having one hydrogen atom removedtherefrom, such as a phenyl group, a biphenyl group, a fluorenyl group,a naphthyl group, an anthryl group or a phenanthryl group; and analkylaryl group such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethylgroup, or a 2-naphthylethyl group. The alkyl chain within the arylalkylgroup preferably has 1 to 4 carbon atom, more preferably 1 or 2, andmost preferably 1.

The aromatic hydrocarbon group may have a substituent. For example, partof the carbon atoms constituting the aromatic ring within the aromatichydrocarbon group may be substituted with a hetero atom, or a hydrogenatom bonded to the aromatic ring within the aromatic hydrocarbon groupmay be substituted with a substituent.

In the former example, a heteroaryl group in which part of the carbonatoms constituting the ring within the aforementioned aryl group hasbeen substituted with a hetero atom such as an oxygen atom, a sulfuratom or a nitrogen atom, and a heteroarylalkyl group in which part ofthe carbon atoms constituting the aromatic hydrocarbon ring within theaforementioned arylalkyl group has been substituted with theaforementioned heteroatom can be used.

In the latter example, as the substituent for the aromatic hydrocarbongroup, an alkyl group, an alkoxy group, a halogen atom, a halogenatedalkyl group, a hydroxyl group, an oxygen atom (═O) or the like can beused.

The alkyl group as the substituent for the aromatic hydrocarbon group ispreferably an alkyl group of 1 to 5 carbon atoms, and a methyl group, anethyl group, a propyl group, an n-butyl group or a tert-butyl group isparticularly desirable.

The alkoxy group as the substituent for the aromatic hydrocarbon groupis preferably an alkoxy group having 1 to 5 carbon atoms, morepreferably a methoxy group, ethoxy group, n-propoxy group, iso-propoxygroup, n-butoxy group or tert-butoxy group, and most preferably amethoxy group or an ethoxy group.

Examples of the halogen atom as the substituent for the aromatichydrocarbon group include a fluorine atom, a chlorine atom, a bromineatom and an iodine atom, and a fluorine atom is preferable.

Example of the halogenated alkyl group as the substituent for thearomatic hydrocarbon group includes a group in which part or all of thehydrogen atoms within the aforementioned alkyl group have beensubstituted with the aforementioned halogen atoms.

The aliphatic hydrocarbon group for X may be either a saturatedaliphatic hydrocarbon group, or an unsaturated aliphatic hydrocarbongroup. Further, the aliphatic hydrocarbon group may be linear, branchedor cyclic.

In the aliphatic hydrocarbon group for X, a part of the carbon atomsconstituting the aliphatic hydrocarbon group may be substituted with asubstituent group containing a hetero atom, or a part or all of thehydrogen atoms constituting the aliphatic hydrocarbon group may besubstituted with a substituent group containing a hetero atom.

As the “hetero atom” for X, there is no particular limitation as long asit is an atom other than a carbon atom and a hydrogen atom. Examples ofhetero atoms include a halogen atom, an oxygen atom, a sulfur atom and anitrogen atom. Examples of the halogen atom include a fluorine atom, achlorine atom, an iodine atom and a bromine atom.

The substituent group containing a hetero atom may consist of a heteroatom, or may be a group containing a group or atom other than a heteroatom.

Specific examples of the substituent group for substituting part of thecarbon atoms include —O—, —C(═O)—O—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—,—NH— (the H may be replaced with a substituent such as an alkyl group oran acyl group), —S—, —S(═O)₂— and —S(═O)₂—O—. When the aliphatichydrocarbon group is cyclic, the aliphatic hydrocarbon group may containany of these substituent groups in the ring structure.

Examples of the substituent group for substituting part or all of thehydrogen atoms include an alkoxy group, a halogen atom, a halogenatedalkyl group, a hydroxyl group, an oxygen atom (═O) and a cyano group.

The aforementioned alkoxy group is preferably an alkoxy group having 1to 5 carbon atoms, more preferably a methoxy group, ethoxy group,n-propoxy group, iso-propoxy group, n-butoxy group or tert-butoxy group,and most preferably a methoxy group or an ethoxy group.

Examples of the aforementioned halogen atom include a fluorine atom, achlorine atom, a bromine atom and an iodine atom, and a fluorine atom ispreferable.

Example of the aforementioned halogenated alkyl group includes a groupin which part or all of the hydrogen atoms within an alkyl group of 1 to5 carbon atoms (e.g., a methyl group, an ethyl group, a propyl group, ann-butyl group or a tert-butyl group) have been substituted with theaforementioned halogen atoms.

As the aliphatic hydrocarbon group, a linear or branched saturatedhydrocarbon group, a linear or branched monovalent unsaturatedhydrocarbon group, or a cyclic aliphatic hydrocarbon group (aliphaticcyclic group) is preferable.

The linear saturated hydrocarbon group (alkyl group) preferably has 1 to20 carbon atoms, more preferably 1 to 15, and most preferably 1 to 10.Specific examples include a methyl group, an ethyl group, a propylgroup, a butyl group, a pentyl group, a hexyl group, a heptyl group, anoctyl group, a nonyl group, a decanyl group, an undecyl group, a dodecylgroup, a tridecyl group, an isotridecyl group, a tetradecyl group, apentadecyl group, a hexadecyl group, an isohexadecyl group, a heptadecylgroup, an octadecyl group, a nonadecyl group, an icosyl group, ahenicosyl group and a docosyl group.

The branched saturated hydrocarbon group (alkyl group) preferably has 3to 20 carbon atoms, more preferably 3 to 15, and most preferably 3 to10. Specific examples include a 1-methylethyl group, a 1-methylpropylgroup, a 2-methylpropyl group, a 1-methylbutyl group, a 2-methylbutylgroup, a 3-methylbutyl group, a 1-ethylbutyl group, a 2-ethylbutylgroup, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentylgroup and a 4-methylpentyl group.

The unsaturated hydrocarbon group preferably has 2 to 10 carbon atoms,more preferably 2 to 5, still more preferably 2 to 4, and mostpreferably 3. Examples of linear monovalent unsaturated hydrocarbongroups include a vinyl group, a propenyl group (an allyl group) and abutynyl group. Examples of branched monovalent unsaturated hydrocarbongroups include a 1-methylpropenyl group and a 2-methylpropenyl group.

Among the above-mentioned examples, as the unsaturated hydrocarbongroup, a propenyl group is particularly desirable.

The aliphatic cyclic group may be either a monocyclic group or apolycyclic group. The aliphatic cyclic group preferably has 3 to 30carbon atoms, more preferably 5 to 30, still more preferably 5 to 20,still more preferably 6 to 15, and most preferably 6 to 12.

As the aliphatic cyclic group, a group in which one or more hydrogenatoms have been removed from a monocycloalkane or a polycycloalkane suchas a bicycloalkane, tricycloalkane or tetracycloalkane can be used.Specific examples include groups in which one or more hydrogen atomshave been removed from a monocycloalkane such as cyclopentane orcyclohexane; and groups in which one or more hydrogen atoms have beenremoved from a polycycloalkane such as adamantane, norbornane,isobornane, tricyclodecane or tetracyclododecane.

When the aliphatic cyclic group does not contain a heteroatom-containing substituent group in the ring structure thereof, thealiphatic cyclic group is preferably a polycyclic group, more preferablya group in which one or more hydrogen atoms have been removed from apolycycloalkane, and a group in which one or more hydrogen atoms havebeen removed from adamantane is particularly desirable.

When the aliphatic cyclic group contains a hetero atom-containingsubstituent group in the ring structure thereof, the heteroatom-containing substituent group is preferably —O—, —C(═O)—O—, —S—,—S(═O)₂— or —S(═O)₂—O—. Specific examples of such aliphatic cyclicgroups include groups represented by formulas (L1) to (L5) and (S1) to(S4) shown below.

In the formula, Q″ represents an alkylene group of 1 to 5 carbon atoms,—O—, —S—, —O—R⁹⁴— or —S—R⁹⁵— (wherein each of R⁹⁴ and R⁹⁵ independentlyrepresents an alkylene group of 1 to 5 carbon atoms); and m represents 0or 1.

As the alkylene group for Q″, R⁹⁴ and R⁹⁵, the same alkylene groups asthose described above for R⁹¹ to R⁹³ can be used.

In these aliphatic cyclic groups, part of the hydrogen atoms bonded tothe carbon atoms constituting the ring structure may be substituted witha substituent. Examples of substituents include an alkyl group, analkoxy group, a halogen atom, a halogenated alkyl group, a hydroxylgroup and an oxygen atom (═O).

As the alkyl group, an alkyl group of 1 to 5 carbon atoms is preferable,and a methyl group, an ethyl group, a propyl group, an n-butyl group ora tert-butyl group is particularly desirable.

As the alkoxy group and the halogen atom, the same groups as thesubstituent groups for substituting part or all of the hydrogen atomscan be used.

In the present invention, as X, a cyclic group which may have asubstituent is preferable. The cyclic group may be either an aromatichydrocarbon group which may have a substituent, or an aliphatic cyclicgroup which may have a substituent, and an aliphatic cyclic group whichmay have a substituent is preferable.

As the aromatic hydrocarbon group, a naphthyl group which may have asubstituent, or a phenyl group which may have a substituent ispreferable.

As the aliphatic cyclic group which may have a substituent, an aliphaticpolycyclic group which may have a substituent is preferable. As thealiphatic polycyclic group, the aforementioned group in which one ormore hydrogen atoms have been removed from a polycycloalkane, and groupsrepresented by formulas (L2) to (L5), (S3) and (S4) are preferable.

In the present invention, R⁴″ preferably has X-Q¹- as a substituent. Insuch a case, R⁴″ is preferably a group represented by the formulaX-Q¹-Y¹— (in the formula, Q¹ and X are the same as defined above; and Y¹represents an alkylene group of 1 to 4 carbon atoms which may have asubstituent, or a fluorinated alkylene group of 1 to 4 carbon atomswhich may have a substituent).

In the group represented by the formula X-Q¹-Y¹—, as the alkylene groupfor Y¹, the same alkylene group as those described above for Q¹ in whichthe number of carbon atoms is 1 to 4 can be used.

As the fluorinated alkylene group, the aforementioned alkylene group inwhich part or all of the hydrogen atoms has been substituted withfluorine atoms can be used.

Specific examples of Y¹ include —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂—,—CF(CF₃)CF₂—, —CF(CF₂CF₃)—, —C(CF₃)₂—, —CF₂CF₂CF₂CF₂—, —CF(CF₃)CF₂CF₂—,—CF₂CF(CF₃)CF₂—, —CF(CF₃)CF(CF₃)—, —C(CF₃)₂CF₂—, —CF(CF₂CF₃)CF₂—,—CF(CF₂CF₂CF₃)—, —C(CF₃)(CF₂CF₃)—; —CHF—, —CH₂CF₂—, —CH₂CH₂CF₂—,—CH₂CF₂CF₂—, —CH(CF₃)CH₂—, —CH(CF₂CF₃)—, —C(CH₃)(CF₃)—, —CH₂CH₂CH₂CF₂—,—CH₂CH₂CF₂CF₂—, —CH(CF₃)CH₂CH₂—, —CH₂CH(CF₃)CH₂—, —CH(CF₃)CH(CF₃)—,—C(CF₃)₂CH₂—; —CH₂—, —CH₂CH₂—, —CH₂CH₂CH₂—, —CH(CH₃)CH₂—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —CH₂CH₂CH₂CH₂—, —CH(CH₃)CH₂CH₂—, —CH₂CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, —CH(CH₂CH₂CH₃)—, and—C(CH₃)(CH₂CH₃)—.

Y¹ is preferably a fluorinated alkylene group, and particularlypreferably a fluorinated alkylene group in which the carbon atom bondedto the adjacent sulfur atom is fluorinated. Examples of such fluorinatedalkylene groups include —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂—, —CF(CF₃)CF₂—,—CF₂CF₂CF₂CF₂—, —CF(CF₃)CF₂CF₂—, —CF₂CF(CF₃)CF₂—, —CF(CF₃)CF(CF₃)—,—C(CF₃)₂CF₂—, —CF(CF₂CF₃)CF₂—; —CH₂CF₂—, —CH₂CH₂CF₂—, —CH₂CF₂CF₂—;—CH₂CH₂CH₂CF₂—, —CH₂CH₂CF₂CF₂—, and —CH₂CF₂CF₂CF₂—.

Of these, —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂— or CH₂CF₂CF₂— is preferable,—CF₂—, —CF₂CF₂— or —CF₂CF₂CF₂— is more preferable, and —CF₂— isparticularly desirable.

The alkylene group or fluorinated alkylene group may have a substituent.The alkylene group or fluorinated alkylene group “has a substituent”means that part or all of the hydrogen atoms or fluorine atoms in thealkylene group or fluorinated alkylene group has been substituted withgroups other than hydrogen atoms and fluorine atoms.

Examples of substituents which the alkylene group or fluorinatedalkylene group may have include an alkyl group of 1 to 4 carbon atoms,an alkoxy group of 1 to 4 carbon atoms, and a hydroxyl group.

In formula (b-2), R⁵″ and R⁶″ each independently represent an aryl groupor alkyl group. At least one of R⁵″ and R⁶″ represents an aryl group. Itis preferable that both of R⁵″ and R⁶″ represent an aryl group.

As the aryl group for R⁵″ and R⁶″, the same as the aryl groups for R¹″to R³″ can be used.

As the alkyl group for R⁵″ and R⁶″, the same as the alkyl groups for R¹″to R³″ can be used.

It is particularly desirable that both of R⁵″ and R⁶″ represents aphenyl group.

As R⁴′ in formula (b-2), the same groups as those mentioned above forR⁴″ in formula (b-1) can be used.

Specific examples of suitable onium salt acid generators represented byformula (b-1) or (b-2) include diphenyliodoniumtrifluoromethanesulfonate or nonafluorobutanesulfonate;bis(4-tert-butylphenyl)iodonium trifluoromethanesulfonate ornonafluorobutanesulfonate; triphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;tri(4-methylphenyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;dimethyl(4-hydroxynaphthyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;monophenyldimethylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;diphenylmonomethylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;(4-methylphenyl)diphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;(4-methoxyphenyl)diphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;tri(4-tert-butyl)phenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;diphenyl(1-(4-methoxy)naphthyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;di(1-naphthyl)phenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;1-phenyltetrahydrothiophenium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;1-(4-methylphenyl)tetrahydrothiophenium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;1-(3,5-dimethyl-4-hydroxyphenyl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(4-methoxynaphthalene-1-yl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(4-ethoxynaphthalene-1-yl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(4-n-butoxynaphthalene-1-yl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate; 1-phenyltetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate; 1-(4-hydroxyphenyl)tetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(3,5-dimethyl-4-hydroxyphenyl)tetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate; and 1-(4-methylphenyl)tetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate.

It is also possible to use onium salts in which the anion moiety ofthese onium salts is replaced by an alkyl sulfonate such asmethanesulfonate, n-propanesulfonate, n-butanesulfonate,n-octanesulfonate, 1-adamantanesulfonate, or 2-norbornanesulfonate,d-camphor-10-sulfonate, benzenesulfonate, perfluorobenzenesulfonate, orp-toluenesulfonate.

Furthermore, onium salts in which the anion moiety of these onium saltsare replaced by an anion moiety represented by any one of formulas (b1)to (b8) shown below can be used.

In the formulas, p represents an integer of 1 to 3; each of q0 to q2independently represents an integer of 1 to 5; q3 represents an integerof 1 to 12; each of r1 and r2 independently represents an integer of 0to 3; g represents an integer of 1 to 20; t3 represents an integer of 1to 3; R⁷ represents a substituent; and R⁸ represents a hydrogen atom, analkyl group of 1 to 5 carbon atoms or a halogenated alkyl group of 1 to5 carbon atoms.

In the formulas, p, R⁷ and Q″ are the same as defined above; each of n1to n5 independently represents 0 or 1; each of v1 to v5 independentlyrepresents an integer of 0 to 3; and each of w1 to w5 independentlyrepresents an integer of 0 to 3.

As the substituent for R⁷, the same groups as those which theaforementioned aliphatic hydrocarbon group or aromatic hydrocarbon groupfor X may have as a substituent can be used.

If there are two or more of the R⁷ group, as indicated by the values r1,r2, and w1 to w5, then the two or more of the R⁷ groups may be the sameor different from each other.

R⁸ represents a hydrogen atom, an alkyl group of 1 to 5 carbon atoms ora halogenated alkyl group of 1 to 5 carbon atoms. As the alkyl group andthe halogenated alkyl group, the same alkyl groups and halogenated alkylgroups as those described above for R can be mentioned.

Each of q0 to q2, r1, r2 and w1 to w5 is preferably an integer of 0 to2, and more preferably 0 or 1.

t3 is preferably 1 or 2, and most preferably 1.

q3 is preferably 1 to 5, more preferably 1 to 3, and most preferably 1.

Further, onium salt-based acid generators in which the anion moiety ingeneral formula (b-1) or (b-2) is replaced by an anion moietyrepresented by general formula (b-3) or (b-4) shown below (the cationmoiety is the same as (b-1) or (b-2)) may be used.

In the formulas, X″ represents an alkylene group of 2 to 6 carbon atomsin which at least one hydrogen atom has been substituted with a fluorineatom; and each of Y″ and Z″ independently represents an alkyl group of 1to 10 carbon atoms in which at least one hydrogen atom has beensubstituted with a fluorine atom.

X″ represents a linear or branched alkylene group in which at least onehydrogen atom has been substituted with a fluorine atom, and thealkylene group has 2 to 6 carbon atoms, preferably 3 to 5 carbon atoms,and most preferably 3 carbon atoms.

Each of Y″ and Z″ independently represents a linear or branched alkylgroup in which at least one hydrogen atom has been substituted with afluorine atom, and the alkyl group has 1 to 10 carbon atoms, preferably1 to 7 carbon atoms, and most preferably 1 to 3 carbon atoms.

The smaller the number of carbon atoms of the alkylene group for X″ orthose of the alkyl group for Y″ and Z″ within the above-mentioned rangeof the number of carbon atoms, the more the solubility in a resistsolvent is improved.

Further, in the alkylene group for X″ or the alkyl group for Y″ and Z″,it is preferable that the number of hydrogen atoms substituted withfluorine atoms is as large as possible because the acid strengthincreases and the transparency to high energy radiation of 200 nm orless or electron beam is improved. The fluorination ratio of thealkylene group or alkyl group is preferably from 70 to 100%, morepreferably from 90 to 100%, and it is particularly desirable that thealkylene group or alkyl group be a perfluoroalkylene group orperfluoroalkyl group in which all hydrogen atoms are substituted withfluorine atoms.

Further, it is possible to use an onium salt-based acid generatorrepresented by general formula (b-1) or (b2) in which the anion moiety(R⁴″SO₃ ⁻) has been replaced by R⁷″—COO⁻ (in the formula, R⁷″ representsan alkyl group or a fluorinated alkyl group) (the cation moiety is thesame as (b-1) or (b-2)).

As R^(7″), the same groups as those described above for R⁴″ can be used.

Specific examples of the group represented by the formula “R⁷″—COO⁻”include a trifluoroacetate ion, an acetate ion, and a1-adamantanecarboxylic acid ion.

Furthermore, as an onium salt-based acid generator, a sulfonium salthaving a cation moiety represented by general formula (b-5) or (b-6)shown below may be used.

In the formulas, each of R⁴¹ to R⁴⁶ independently represents an alkylgroup, an acetyl group, an alkoxy group, a carboxy group, a hydroxylgroup or a hydroxyalkyl group; each of n₁ to n₅ independently representsan integer of 0 to 3; n₆ represents an integer of 0 to 2; and Grepresents a single bond, a methylene group, a sulfur atom, an oxygenatom, a nitrogen atom, a carbonyl group, —SO—, —SO₃—, —COO—, —CONH— or—N(R_(N))— (R_(N) represents an alkyl group of 1 to 5 carbon atoms).

With respect to R⁴¹ to R⁴⁶, the alkyl group is preferably an alkyl groupof 1 to 5 carbon atoms, more preferably a linear or branched alkylgroup, and most preferably a methyl group, ethyl group, propyl group,isopropyl group, n-butyl group or tert butyl group.

The alkoxy group is preferably an alkoxy group of 1 to 5 carbon atoms,more preferably a linear or branched alkoxy group, and most preferably amethoxy group or ethoxy group.

The hydroxyalkyl group is preferably the aforementioned alkyl group inwhich one or more hydrogen atoms have been substituted with hydroxygroups, and examples thereof include a hydroxymethyl group, ahydroxyethyl group and a hydroxypropyl group.

If there are two or more of an individual R⁴¹ to R⁴⁶ group, as indicatedby the corresponding value of n₁ to n₆, then the two or more of theindividual R⁴¹ to R⁴⁶ group may be the same or different from eachother.

n₁ is preferably 0 to 2, more preferably 0 or 1, and still morepreferably 0.

It is preferable that n₂ and n₃ each independently represent 0 or 1, andmore preferably 0.

n₄ is preferably 0 to 2, and more preferably 0 or 1.

n₅ is preferably 0 or 1, and more preferably 0.

n₆ is preferably 0 or 1, and more preferably 1.

The anion moiety of the sulfonium salt having a cation moietyrepresented by general formula (b-5) or (b-6) is not particularlylimited, and the same anion moieties for onium salt-based acidgenerators which have been proposed may be used. Examples of such anionmoieties include fluorinated alkylsulfonic acid ions such as anionmoieties (R⁴″SO₃ ⁻) for onium salt-based acid generators represented bygeneral formula (b-1) or (b-2) shown above; and anion moietiesrepresented by general formula (b-3) or (b-4) shown above.

In the present description, an oximesulfonate-based acid generator is acompound having at least one group represented by general formula (B-1)shown below, and has a feature of generating acid by irradiation. Suchoximesulfonate acid generators are widely used for a chemicallyamplified resist composition, and can be appropriately selected.

In the formula, each of R³¹ and R³² independently represents an organicgroup.

The organic group for R³¹ and R³² refers to a group containing a carbonatom, and may include atoms other than carbon atoms (e.g., a hydrogenatom, an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom(such as a fluorine atom and a chlorine atom) and the like).

As the organic group for R³¹, a linear, branched, or cyclic alkyl groupor aryl group is preferable. The alkyl group or the aryl group may havea substituent. The substituent is not particularly limited, and examplesthereof include a fluorine atom and a linear, branched, or cyclic alkylgroup having 1 to 6 carbon atoms. The alkyl group or the aryl group “hasa substituent” means that part or all of the hydrogen atoms of the alkylgroup or the aryl group is substituted with a substituent.

The alkyl group preferably has 1 to 20 carbon atoms, more preferably 1to 10 carbon atoms, still more preferably 1 to 8 carbon atoms, stillmore preferably 1 to 6 carbon atoms, and most preferably 1 to 4 carbonatoms. As the alkyl group, a partially or completely halogenated alkylgroup (hereinafter, sometimes referred to as a “halogenated alkylgroup”) is particularly desirable. The “partially halogenated alkylgroup” refers to an alkyl group in which part of the hydrogen atoms aresubstituted with halogen atoms and the “completely halogenated alkylgroup” refers to an alkyl group in which all of the hydrogen atoms aresubstituted with halogen atoms. Examples of halogen atoms includefluorine atoms, chlorine atoms, bromine atoms and iodine atoms, andfluorine atoms are particularly desirable. In other words, thehalogenated alkyl group is preferably a fluorinated alkyl group.

The aryl group preferably has 4 to 20 carbon atoms, more preferably 4 to10 carbon atoms, and most preferably 6 to 10 carbon atoms. As the arylgroup, partially or completely halogenated aryl group is particularlydesirable. The “partially halogenated aryl group” refers to an arylgroup in which some of the hydrogen atoms are substituted with halogenatoms and the “completely halogenated aryl group” refers to an arylgroup in which all of hydrogen atoms are substituted with halogen atoms.

As R³¹, an alkyl group of 1 to 4 carbon atoms which has no substituentor a fluorinated alkyl group of 1 to 4 carbon atoms is particularlydesirable.

As the organic group for R³², a linear, branched, or cyclic alkyl group,aryl group, or cyano group is preferable. Examples of the alkyl groupand the aryl group for R³² include the same alkyl groups and aryl groupsas those described above for R³¹.

As R³², a cyano group, an alkyl group of 1 to 8 carbon atoms having nosubstituent or a fluorinated alkyl group of 1 to 8 carbon atoms isparticularly desirable.

Preferred examples of the oxime sulfonate acid generator includecompounds represented by general formula (B-2) or (B-3) shown below.

In the formula, R³³ represents a cyano group, an alkyl group having nosubstituent or a halogenated alkyl group; R³⁴ represents an aryl group;and R³⁵ represents an alkyl group having no substituent or a halogenatedalkyl group.

In the formula, R³⁶ represents a cyano group, an alkyl group having nosubstituent or a halogenated alkyl group; R³⁷ represents a divalent ortrivalent aromatic hydrocarbon group; R³⁸ represents an alkyl grouphaving no substituent or a halogenated alkyl group; and p″ represents 2or 3.

In general formula (B-2), the alkyl group having no substituent or thehalogenated alkyl group for R³³ preferably has 1 to 10 carbon atoms,more preferably 1 to 8 carbon atoms, and most preferably 1 to 6 carbonatoms.

As R³³, a halogenated alkyl group is preferable, and a fluorinated alkylgroup is more preferable.

The fluorinated alkyl group for R³³ preferably has 50% or more of thehydrogen atoms thereof fluorinated, more preferably 70% or more, andmost preferably 90% or more.

Examples of the aryl group for R³⁴ include groups in which one hydrogenatom has been removed from an aromatic hydrocarbon ring, such as aphenyl group, a biphenyl group, a fluorenyl group, a naphthyl group, ananthryl group, and a phenanthryl group, and heteroaryl groups in whichsome of the carbon atoms constituting the ring(s) of these groups aresubstituted with hetero atoms such as an oxygen atom, a sulfur atom, anda nitrogen atom. Of these, a fluorenyl group is preferable.

The aryl group for R³⁴ may have a substituent such as an alkyl group of1 to 10 carbon atoms, a halogenated alkyl group, or an alkoxy group. Thealkyl group and halogenated alkyl group as the substituent preferablyhas 1 to 8 carbon atoms, and more preferably 1 to 4 carbon atoms.Further, the halogenated alkyl group is preferably a fluorinated alkylgroup.

The alkyl group having no substituent or the halogenated alkyl group forR³⁵ preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbonatoms, and most preferably 1 to 6 carbon atoms.

As R³⁵, a halogenated alkyl group is preferable, and a fluorinated alkylgroup is more preferable.

In terms of enhancing the strength of the acid generated, thefluorinated alkyl group for R³⁵ preferably has 50% or more of thehydrogen atoms fluorinated, more preferably 70% or more, still morepreferably 90% or more. A completely fluorinated alkyl group in which100% of the hydrogen atoms are substituted with fluorine atoms isparticularly desirable.

In general formula (B-3), as the alkyl group having no substituent andthe halogenated alkyl group for R³⁶, the same alkyl group having nosubstituent and the halogenated alkyl group described above for R³³ canbe used.

Examples of the divalent or trivalent aromatic hydrocarbon group for R³⁷include groups in which one or two hydrogen atoms have been removed fromthe aryl group for R³⁴.

As the alkyl group having no substituent or the halogenated alkyl groupfor R³⁸, the same one as the alkyl group having no substituent or thehalogenated alkyl group for R³⁵ can be used.

p″ is preferably 2.

Specific examples of suitable oxime sulfonate acid generators includeα-(p-toluenesulfonyloxyimino)-benzyl cyanide,α-(p-chlorobenzenesulfonyloxyimino)-benzyl cyanide,α-(4-nitrobenzenesulfonyloxyimino)-benzyl cyanide,α-(4-nitro-2-trifluoromethylbenzenesulfonyloxyimino)-benzyl cyanide,α-(benzenesulfonyloxyimino)-4-chlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-2,4-dichlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-2,6-dichlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-4-methoxybenzyl cyanide,α-(2-chlorobenzenesulfonyloxyimino)-4-methoxybenzyl cyanide,α-(benzenesulfonyloxyimino)-thien-2-yl acetonitrile,α-(4-dodecylbenzenesulfonyloxyimino)benzyl cyanide,α-[(p-toluenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,α-[(dodecylbenzenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,α-(tosyloxyimino)-4-thienyl cyanide,α-(methylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cycloheptenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cyclooctenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-cyclohexyl acetonitrile,α-(ethylsulfonyloxyimino)-ethyl acetonitrile,α-(propylsulfonyloxyimino)-propyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-cyclopentyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-cyclohexyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(ethylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(n-butylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(ethylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(n-butylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(methylsulfonyloxyimino)-phenyl acetonitrile,α-(methylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-phenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(ethylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(propylsulfonyloxyimino)-p-methylphenyl acetonitrile, andα-(methylsulfonyloxyimino)-p-bromophenyl acetonitrile.

Further, oxime sulfonate-based acid generators disclosed in JapaneseUnexamined Patent Application, First Publication No. Hei 9-208554(Chemical Formulas 18 and 19 shown in paragraphs [0012] to [0014]) andoxime sulfonate-based acid generators disclosed in WO 2004/074242A2(Examples 1 to 40 described at pages 65 to 85) may be preferably used.

Furthermore, as preferable examples, the following can be used.

Of the aforementioned diazomethane acid generators, specific examples ofsuitable bisalkyl or bisaryl sulfonyl diazomethanes includebis(isopropylsulfonyl)diazomethane, bis(p-toluenesulfonyl)diazomethane,bis(1,1-dimethylethylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane, andbis(2,4-dimethylphenylsulfonyl)diazomethane.

Further, diazomethane acid generators disclosed in Japanese UnexaminedPatent Application, First Publication No. Hei 11-035551, JapaneseUnexamined Patent Application, First Publication No. Hei 11-035552 andJapanese Unexamined Patent Application, First Publication No. Hei11-035573 may be preferably used.

Furthermore, as examples of poly(bis-sulfonyl)diazomethanes, thosedisclosed in Japanese Unexamined Patent Application, First PublicationNo. Hei 11-322707, including1,3-bis(phenylsulfonyldiazomethylsulfonyl)propane,1,4-bis(phenylsulfonyldiazomethylsulfonyl)butane,1,6-bis(phenylsulfonyldiazomethylsulfonyl)hexane,1,10-bis(phenylsulfonyldiazomethylsulfonyl)decane,1,2-bis(cyclohexylsulfonyldiazomethylsulfonyl)ethane,1,3-bis(cyclohexylsulfonyldiazomethylsulfonyl)propane,1,6-bis(cyclohexylsulfonyldiazomethylsulfonyl)hexane, and1,10-bis(cyclohexylsulfonyldiazomethylsulfonyl)decane, may be given.

As the component (B), one type of acid generator may be used, or two ormore types of acid generators may be used in combination.

In the present invention, as the component (B), it is preferable to usean onium salt having a fluorinated alkylsulfonic acid ion as the anionmoiety.

In the positive resist composition of the present invention, the amountof the component (B) relative to 100 parts by weight of the component(A) is preferably 0.5 to 50 parts by weight, and more preferably 1 to 40parts by weight. When the amount of the component (B) is within theabove-mentioned range, formation of a resist pattern can besatisfactorily performed. Further, by virtue of the above-mentionedrange, a uniform solution can be obtained and the storage stabilitybecomes satisfactory.

<Optional Components>

The positive resist composition of the present invention may furthercontain a nitrogen-containing organic compound (D) (hereafter referredto as the component (D)) as an optional component.

As the component (D), there is no particular limitation as long as itfunctions as an acid diffusion control agent, i.e., a quencher whichtraps the acid generated from the component (B) upon exposure. Amultitude of these components (D) have already been proposed, and any ofthese known compounds may be used. Examples thereof include an aliphaticamine and an aromatic amine. Among these, an aliphatic amine ispreferable, and a secondary aliphatic amine or tertiary aliphatic amineis particularly desirable. The term “aliphatic cyclic group” refers to amonocyclic group or polycyclic group that has no aromaticity. Analiphatic amine is an amine having one or more aliphatic groups, and thealiphatic groups preferably have 1 to 20 carbon atoms.

Examples of these aliphatic amines include amines in which at least onehydrogen atom of ammonia (NH₃) has been substituted with an alkyl groupor hydroxyalkyl group of no more than 20 carbon atoms (i.e., alkylaminesor alkylalcoholamines), and cyclic amines.

Specific examples of alkylamines and alkylalcoholamines includemonoalkylamines such as n-hexylamine, n-heptylamine, n-octylamine,n-nonylamine, and n-decylamine; dialkylamines such as diethylamine,di-n-propylamine, di-n-heptylamine, di-n-octylamine, anddicyclohexylamine; trialkylamines such as trimethylamine, triethylamine,tri-n-propylamine, tri-n-butylamine, tri-n-hexylamine,tri-n-pentylamine, tri-n-heptylamine, tri-n-octylamine,tri-n-nonylamine, tri-n-decylamine, and tri-n-dodecylamine; and alkylalcohol amines such as diethanolamine, triethanolamine,diisopropanolamine, triisopropanolamine, di-n-octanolamine,tri-n-octanolamine, stearyldiethanolamine and laurildiethanolamine.Among these, trialkylamines and/or alkylalcoholamines are preferable.

Examples of the cyclic amine include heterocyclic compounds containing anitrogen atom as a hetero atom. The heterocyclic compound may be amonocyclic compound (aliphatic monocyclic amine), or a polycycliccompound (aliphatic polycyclic amine).

Specific examples of the aliphatic monocyclic amine include piperidine,and piperazine.

The aliphatic polycyclic amine preferably has 6 to 10 carbon atoms, andspecific examples thereof include 1,5-diazabicyclo[4.3.0]-5-nonene,1,8-diazabicyclo[5.4.0]-7-undecene, hexamethylenetetramine, and1,4-diazabicyclo[2.2.2]octane.

Examples of other aliphatic amines includetris(2-methoxymethoxyethyl)amine, tris{2-(2-methoxyethoxy)ethyl}amine,tris{2-(2-methoxyethoxymethoxy)ethyl}amine, tris{2-(1-methoxyethoxy)ethyl}amine, tris {2-(1-ethoxyethoxy)ethyl}amine,tris{2-(1-ethoxypropoxy)ethyl}amine andtris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine.

Examples of aromatic amines include aniline, pyridine,4-dimethylaminopyridine, pyrrole, indole, pyrazole, imidazole andderivatives thereof, as well as diphenylamine, triphenylamine,tribenzylamine, 2,6-diisopropylaniline, 2,2′-dipyridyl and4,4′-dipyridyl.

These compounds can be used either alone, or in combinations of two ormore different compounds.

The component (D) is typically used in an amount within a range from0.01 to 5.0 parts by weight, relative to 100 parts by weight of thecomponent (A). When the amount of the component (D) is within theabove-mentioned range, the shape of the resist pattern and the postexposure stability of the latent image formed by the pattern-wiseexposure of the resist layer are improved.

Furthermore, in the positive resist composition of the presentinvention, for preventing any deterioration in sensitivity, andimproving the resist pattern shape and the post exposure stability ofthe latent image formed by the pattern-wise exposure of the resistlayer, at least one compound (E) (hereafter referred to as the component(E)) selected from the group consisting of an organic carboxylic acid,or a phosphorus oxo acid or derivative thereof can be added.

Examples of suitable organic carboxylic acids include acetic acid,malonic acid, citric acid, malic acid, succinic acid, benzoic acid, andsalicylic acid.

Examples of phosphorus oxo acids or derivatives thereof includephosphoric acid, phosphonic acid and phosphinic acid. Among these,phosphonic acid is particularly desirable.

Examples of oxo acid derivatives include esters in which a hydrogen atomwithin the above-mentioned oxo acids is substituted with a hydrocarbongroup. Examples of the hydrocarbon group include an alkyl group of 1 to5 carbon atoms and an aryl group of 6 to 15 carbon atoms.

Examples of phosphoric acid derivatives include phosphoric acid esterssuch as di-n-butyl phosphate and diphenyl phosphate.

Examples of phosphonic acid derivatives include phosphonic acid esterssuch as dimethyl phosphonate, di-n-butyl phosphonate, phenylphosphonicacid, diphenyl phosphonate and dibenzyl phosphonate.

Examples of phosphinic acid derivatives include phosphinic acid esterssuch as phenylphosphinic acid.

As the component (E), one type may be used alone, or two or more typesmay be used in combination.

The component (E) is typically used in an amount within a range from0.01 to 5.0 parts by weight, relative to 100 parts by weight of thecomponent (A).

If desired, other miscible additives can also be added to the positiveresist composition of the present invention. Examples of such miscibleadditives include additive resins for improving the performance of theresist film, surfactants for improving the applicability, dissolutioninhibitors, plasticizers, stabilizers, colorants, halation preventionagents, and dyes.

The positive resist composition of the present invention can be preparedby dissolving the materials for the resist composition in an organicsolvent (hereafter, frequently referred to as “component (S)”).

The component (S) may be any organic solvent which can dissolve therespective components to give a uniform solution, and one or more kindsof any organic solvent can be appropriately selected from those whichhave been conventionally known as solvents for a chemically amplifiedresist.

Examples thereof include lactones such as γ-butyrolactone;

ketones such as acetone, methyl ethyl ketone, cyclohexanone,methyl-n-pentyl ketone, methyl isopentyl ketone, and 2-heptanone;

polyhydric alcohols, such as ethylene glycol, diethylene glycol,propylene glycol and dipropylene glycol;

compounds having an ester bond, such as ethylene glycol monoacetate,diethylene glycol monoacetate, propylene glycol monoacetate, anddipropylene glycol monoacetate; polyhydric alcohol derivatives includingcompounds having an ether bond, such as a monoalkylether (e.g.,monomethylether, monoethylether, monopropylether or monobutylether) ormonophenylether of any of these polyhydric alcohols or compounds havingan ester bond (among these, propylene glycol monomethyl ether acetate(PGMEA) and propylene glycol monomethyl ether (PGME) are preferable);

cyclic ethers such as dioxane; esters such as methyl lactate, ethyllactate (EL), methyl acetate, ethyl acetate, butyl acetate, methylpyruvate, ethyl pyruvate, methyl methoxypropionate, and ethylethoxypropionate;

and aromatic organic solvents such as anisole, ethylbenzylether,cresylmethylether, diphenylether, dibenzylether, phenetole,butylphenylether, ethylbenzene, diethylbenzene, pentylbenzene,isopropylbenzene, toluene, xylene, cymene and mesitylene.

These solvents can be used individually, or in combination as a mixedsolvent.

Among these, propylene glycol monomethyl ether acetate (PGMEA),propylene glycol monomethyl ether (PGME) and ethyl lactate (EL) arepreferable.

Further, among the mixed solvents, a mixed solvent obtained by mixingPGMEA with a polar solvent is preferable. The mixing ratio (weightratio) of the mixed solvent can be appropriately determined, taking intoconsideration the compatibility of the PGMEA with the polar solvent, butis preferably in the range of 1:9 to 9:1, more preferably from 2:8 to8:2.

Specifically, when EL is mixed as the polar solvent, the PGMEA:EL weightratio is preferably from 1:9 to 9:1, and more preferably from 2:8 to8:2. Alternatively, when PGME is mixed as the polar solvent, thePGMEA:PGME is preferably from 1:9 to 9:1, more preferably from 2:8 to8:2, and still more preferably 3:7 to 7:3.

Further, as the component (S), a mixed solvent of at least one of PGMEAand EL with γ-butyrolactone is also preferable. The mixing ratio(former:latter) of such a mixed solvent is preferably from 70:30 to95:5.

The amount of the organic solvent is not particularly limited, and isappropriately adjusted to a concentration which enables coating of acoating solution to a substrate, depending on the thickness of thecoating film. In general, the organic solvent is used in an amount suchthat the solid content of the resist composition becomes within therange from 1 to 20% by weight, and preferably from 2 to 15% by weight.

<<Method of Forming a Resist Pattern>>

The method of forming a resist pattern according to the presentinvention includes: applying a positive resist composition of thepresent invention to a substrate to form a resist film on the substrate;conducting exposure of the resist film; and developing the resist filmto form a resist pattern.

More specifically, the method for forming a resist pattern according tothe present invention can be performed, for example, as follows.

More specifically, the method for forming a resist pattern according tothe present invention can be performed, for example, as follows.Firstly, a positive resist composition of the present invention isapplied onto a substrate using a spinner or the like, and a prebake(post applied bake (PAB)) is conducted under temperature conditions of80 to 150° C. for 40 to 120 seconds, preferably 60 to 90 seconds to forma resist film. Then, for example, using an ArF exposure apparatus or thelike, the resist film is selectively exposed with an ArF exposureapparatus, an electron beam exposure apparatus, an EUV exposureapparatus or the like through a mask pattern or directly irradiated withelectron beam without a mask pattern, followed by post exposure bake(PEB) under temperature conditions of 80 to 150° C. for 40 to 120seconds, preferably 60 to 90 seconds. Subsequently, developing isconducted using an alkali developing solution such as a 0.1 to 10% byweight aqueous solution of tetramethylammonium hydroxide (TMAH),preferably followed by rinsing with pure water, and drying. If desired,bake treatment (post bake) can be conducted following the developing.

In this manner, a resist pattern that is faithful to the mask patterncan be obtained.

The substrate is not specifically limited and a conventionally knownsubstrate can be used. For example, substrates for electroniccomponents, and such substrates having wiring patterns formed thereoncan be used. Specific examples of the material of the substrate includemetals such as silicon wafer, copper, chromium, iron and aluminum; andglass. Suitable materials for the wiring pattern include copper,aluminum, nickel, and gold.

Further, as the substrate, any one of the above-mentioned substratesprovided with an inorganic and/or organic film on the surface thereofmay be used. As the inorganic film, an inorganic antireflection film(inorganic BARC) can be used. As the organic film, an organicantireflection film (organic BARC) can be used.

The wavelength to be used for exposure is not particularly limited andthe exposure can be conducted using radiation such as ArF excimer laser,KrF excimer laser, excimer laser, extreme ultraviolet rays (EUV), vacuumultraviolet rays (VUV), electron beam (EB), X-rays, and soft X-rays. Thepositive resist composition of the present invention is effective to KrFexcimer laser, ArF excimer laser, EB and EUV, and particularly effectiveto ArF excimer laser.

The exposure of the resist film can be either a general exposure (dryexposure) conducted in air or an inert gas such as nitrogen, orimmersion exposure (immersion lithography).

In immersion lithography, the region between the resist film and thelens at the lowermost point of the exposure apparatus is pre-filled witha solvent (immersion medium) that has a larger refractive index than therefractive index of air, and the exposure (immersion exposure) isconducted in this state.

The immersion medium preferably exhibits a refractive index larger thanthe refractive index of air but smaller than the refractive index of theresist film to be exposed. The refractive index of the immersion mediumis not particularly limited as long at it satisfies the above-mentionedrequirements.

Examples of this immersion medium which exhibits a refractive index thatis larger than the refractive index of air but smaller than therefractive index of the resist film include water, fluorine-based inertliquids, silicon-based solvents and hydrocarbon-based solvents.

Specific examples of the fluorine-based inert liquids include liquidscontaining a fluorine-based compound such as C₃HCl₂F₅, C₄F₉OCH₃,C₄F₉OC₂H₅ or C₅H₃F₇ as the main component, which have a boiling pointwithin a range from 70 to 180° C. and preferably from 80 to 160° C. Afluorine-based inert liquid having a boiling point within theabove-mentioned range is advantageous in that the removal of theimmersion medium after the exposure can be conducted by a simple method.

As a fluorine-based inert liquid, a perfluoroalkyl compound in which allof the hydrogen atoms of the alkyl group are substituted with fluorineatoms is particularly desirable. Examples of these perfluoroalkylcompounds include perfluoroalkylether compounds and perfluoroalkylaminecompounds.

Specifically, one example of a suitable perfluoroalkylether compound isperfluoro(2-butyl-tetrahydrofuran) (boiling point 102° C.), and anexample of a suitable perfluoroalkylamine compound isperfluorotributylamine (boiling point 174° C.).

As the immersion medium, water is preferable in terms of cost, safety,environment and versatility.

By the positive resist composition of the present invention, a resistfilm can be formed on a support such as a substrate with excellentadhesion. Further, by the positive resist composition of the presentinvention, various lithography properties are improved, such as theshape of the resist pattern formed (e.g., circularity of the holes of ahole pattern), in-plane uniformity of the pattern dimensions (CDU), linewidth roughness (LWR), mask reproducibility (e.g., mask error factor(MEF)) and the like. LWR refers to the phenomenon in which the linewidths of a line pattern formed using a resist composition becomesheterogeneous, and improvement in this characteristic becomes moreimportant as the pattern becomes finer. The MEF is a parameter thatindicates how faithfully mask patterns of differing dimensions can bereproduced by using the same exposure dose with fixed pitch and changingthe mask size (i.e., mask reproducibility).

In the present invention, the reasons why the above-mentioned effectscan be achieved have not been elucidated yet. However, one of thereasons is presumed that by virtue of the structural unit (a0) having acyclic group containing —SO₄— (which is a polar group) on the terminalof a relatively long side chain, the component (B) can be uniformlydistributed, thereby resulting in the improvement in lithographyproperties.

Further, the positive resist composition of the present inventionexhibits an excellent heat resistance.

When the amount of the structural unit (a3) within the component (A1) isless than the predetermined amount, a resist film formed using thepositive resist composition exhibits a poor heat resistance, and thebaking conditions during the formation of a pattern is limited. Morespecifically, when the heat resistance is poor, the baking temperaturecannot be satisfactorily raised to obtain the desired lithographyproperties, and fluctuation in the dimension of the formed resistpattern is likely to become a problem. For example, when the resistbecomes soft during the post-bake, the resist flows toward the directionof the gap, thereby causing fluctuation of the size of the resistpattern. As a result, the size of the portion where the resist has beenremoved (e.g., diameter of a hole pattern or the space width of a spacepattern) becomes small. It is presumed that such a poor heat resistanceis due to the fact that the structural unit (a0) has a relatively longside chain.

In the present invention, by using the structural unit (a0) incombination with the structural unit (a3) in a specific amount, it ispresumed that an interaction occurs, which results in the improvement ofthe heat resistance.

EXAMPLES

As follows is a description of examples of the present invention,although the scope of the present invention is by no way limited bythese examples.

In the following examples, a unit represented by a chemical formula (01)is designated as “compound (01)”, and the same applies for compoundsrepresented by other formulas.

The polymeric compounds 1 to 25 used as the base component in thepresent examples were synthesized in accordance with the followingPolymer Synthesis Examples 2, 3, 1 and 4 to 25, respectively.

The compounds (B)-1 and (B)-2 used as the acid-generator component inthe present examples were synthesized in accordance with the followingAcid-generator Synthesis Examples 1 and 2.

The monomers used in the following polymer synthesis examples are shownbelow. Among these, compounds (01), (02) and (13) were synthesized inaccordance with the following Monomer Synthesis Examples 1 to 3.

Monomer Synthesis Example 1 Synthesis of Compound (01)

The compound (01) used in the polymer synthesis examples described laterwas synthesized as follows.

300 ml of a THF solution containing 20 g (105.14 mmol) of an alcohol(1), 30.23 g (157.71 mmol) of ethyldiisopropylaminocarbodiimide (EDCl)hydrochloride and 0.6 g (5 mmol) of dimethylaminopyridine (DMAP) wasadded to a 500 ml three-necked flask in a nitrogen atmosphere, and 16.67g (115.66 mmol) of a precursor (1) was added thereto while cooling withice (0° C.), followed by stirring at room temperature for 12 hours.

After conducting thin-layer chromatography (TLC) to confirm that the rawmaterials had been consumed, 50 ml of water was added to stop thereaction. Then, the reaction solvent was concentrated under reducedpressure, and extraction was conducted with ethyl acetate three times.The obtained organic phase was washed with water, saturated sodiumhydrogencarbonate and 1N-HClaq in this order. Thereafter, the solventwas distilled off under reduced pressure, and the resulting product wasdried, thereby obtaining the compound (01).

The results of instrumental analysis of the obtained compound (01) wereas follows. From the results, it was confirmed that the compound (01)had a structure shown below.

¹H-NMR (CDCl₃, 400 MHz): δ(ppm)=6.22 (s, 1H, H^(a)), 5.70 (s, 1H,H^(b)), 4.71-4.85 (m, 2H, H^(c,d)), 4.67 (s, 2H, H^(k)), 3.40-3.60 (m,2H, H^(e,f)), 2.58-2.70 (m, 1H, H^(g)), 2.11-2.21 (m, 2H, H^(h)), 2.00(s, 3H, H^(i)), 1.76-2.09 (m, 2H, H^(j)).

Monomer Synthesis Example 2 Synthesis of Compound (02)

In a three-necked flask in a nitrogen atmosphere, 50 g of a precursor(2) and 37.18 g of an alcohol (1) were dissolved in 500 ml oftetrahydrofuran. Then, 56.07 g of ethyldiisopropylaminocarbodiimidehydrochloride (EDCI.HCl) was added thereto, and cooled to 0° C. Then,dimethylaminopyridine (DMAP) was added thereto, and reacted for 10minutes. Thereafter, a reaction was performed for at room temperaturefor 12 hours. After the completion of the reaction, 100 ml of water wasadded, and the resultant was concentrated under reduced pressure. Then,extraction was conducted using ethyl acetate, and the organic phase waswashed with water. Subsequently, the organic phase obtained byextraction with ethyl acetate was washed with an aqueous sodiumhydrogencarbonate solution three times. Next, the organic phase waswashed with water. Then, the organic phase was washed with aqueoushydrochloric acid solution twice. Then, the organic phase was washedwith water three times.

Finally, the resultant was concentrated under reduced pressure, followedby washing with heptane twice and drying, thereby obtaining 58.10 g of acompound (02) as an objective compound.

The results of instrumental analysis of the obtained compound (02) wereas follows. From the results, it was confirmed that the compound (02)had a structure shown below.

¹H-NMR (CDCl₃, 400 MHz): δ(ppm)=6.12 (s, 1H, H^(a)), 5.60 (s, 1H,H^(b)), 4.73-4.71 (m, 2H, H^(c)), 4.34 (s, 4H, H^(d)), 3.55 (m, 1H,H^(e)), 3.48 (m, 1H, H^(f)), 2.68-2.57 (m, 4H, H^(g)), 2.16-1.76 (m, 5H,H^(h)), 1.93 (s, 3H, H^(i)).

Monomer Synthesis Example 3 Synthesis of Compound (13)

165 g (584 mmol) of2-(2-(2-methyl-2-adamantyloxy)-2-oxoethoxy)-2-oxoethanol, 2,000 ml ofTHF, 105 ml (754 mmol) of triethylamine, and 0.165 g (1,000 ppm) ofp-methoxyphenol were added to and dissolved in a 2 L three-neck flaskequipped with a thermometer, a cooling pipe, and a stirrer. Then, 62.7ml (648 mmol) of methacryloyl chloride was gradually added thereto whilecooling in an ice bath. The temperature of the resultant was elevated toroom temperature, and the resultant was stirred for 3 hours.Subsequently, 1,000 ml of diethylether was added thereto, followed bywashing with 200 ml of distilled water 5 times. Thereafter, theextraction liquid was concentrated, thereby obtaining 198 g of anobjective compound (13) in the form of a colorless liquid (yield: 97%,GC purity: 99%).

The results of instrumental analysis of the obtained compound (13) wereas follows.

¹H-NMR (CDCl₃, 400 MHz): δ(ppm)=1.58 (d, J=12.5 Hz, 2H), 1.63 (s, 3H),1.71-1.89 (m, 8H), 1.98 (s, 3H), 2.00 (m, 2H), 2.30 (m, 2H), 4.62 (s,2H), 4.80 (s, 2H), 5.66 (m, 1H), 6.23 (m, 1H).

¹³C-NMR: 18.04, 22.15, 26.42, 27.14, 32.82, 34.38, 36.11, 37.92, 60.44,61.28, 89.42, 126.79, 135.18, 165.61, 166.30, 167.20.

GC-MS: 350 (M+, 1.4%), 206 (0.13%), 149 (47%), 148 (100%), 133 (20%), 69(37%).

From the results shown above, it was confirmed that the obtainedcompound (13) was 2-(2-(2-methyl-2-adamantyloxy)-2-oxoethoxy)-2-oxoethylmethacrylate.

2-(2-(2-methyl-2-adamantyloxy)-2-oxoethoxy)-2-oxoethanol used above wassynthesized as follows.

37.6 g (494 mmol) of glycolic acid, 700 mL of DMF, 86.5 g (626 mmol) ofpotassium carbonate, and 28.3 g (170 mmol) of potassium iodide wereadded to a 2 L three-necked flask equipped with a thermometer, a coolingpipe, and a stirrer, followed by stirring at room temperature for 30minutes. Then, 300 ml of a dimethylformamide solution containing 100 g(412 mmol) of 2-methyl-2-adamantyl chloroacetate was gradually addedthereto. The resultant was heated to 40° C., and stirred for 4 hours.Subsequently, 2,000 ml of diethylether was added to the reactionmixture, followed by filtration. The resulting solution was washed with500 ml of distilled water three times. Then, crystallization wasconducted using a mixed solvent containing 300 ml of toluene and 200 mlof heptane, thereby obtaining 78 g of a product in the form of acolorless solid (yield: 67%, GC purity: 99%).

The results of instrumental analysis of the obtained product were asfollows.

¹H-NMR (CDCl₃, 400 MHz): δ(ppm)=1.59 (d, 2H, J=12.5 Hz), 1.64 (s, 3H),1.71-1.99 (m, 10H), 2.29 (m, 2H), 2.63 (0H, J=5.2 Hz), 4.29 (d, 2H,J=5.2 Hz), 4.67 (s, 2H).

¹³C-NMR: 22.35, 26.56, 27.26, 32.97, 34.54, 36.29, 38.05, 60.54, 61.50,89.87, 165.97, 172.81.

GC-MS: 282 (M+, 0.02%), 165 (0.09%), 149 (40%), 148 (100%), 133 (22%),117 (2.57%), 89 (0.40%).

From the results above, it was confirmed that the obtained product was2-(2-(2-methyl-2-adamantyloxy)-2-oxoethoxy)-2-oxoethanol.

Polymer Synthesis Example 1 Synthesis of Polymeric Compound 3

In a three-necked flask equipped with a thermometer and a reflux tube,11.77 g (69.23 mmol) of a compound (21), 15.00 g (47.47 mmol) of acompound (01), 16.58 g (63.29 mmol) of a compound (11), 4.65 g (27.69mmol) of a compound (12) and 3.27 g (13.85 mmol) of a compound (31) weredissolved in 76.91 g of methyl ethyl ketone (MEK) to obtain a solution.Then, 22.1 mmol of dimethyl 2,2′-azobis(isobutyrate) (V-601) was addedand dissolved in the obtained solution. The resultant was dropwise addedto 42.72 g of MEK heated to 78° C. in a nitrogen atmosphere over 3hours. Thereafter, the reaction solution was heated for 4 hour whilestirring, and then cooled to room temperature. The obtained reactionpolymer solution was dropwise added to an excess amount of n-heptane,and an operation to deposit a polymer was conducted. Thereafter, theprecipitated white powder was separated by filtration, followed bywashing with an n-heptane/isopropylalcohol mixed solvent and drying,thereby obtaining 41 g of a polymeric compound 3 as an objectivecompound.

With respect to the polymeric compound 3, the weight average molecularweight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 7,200, and the dispersity was 1.62. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n/o/p=36/26/17/14/8.

Polymer Synthesis Examples 2 to 4 Synthesis of Polymeric Compounds 1, 2and 4

Polymeric compounds 1 and 2 were synthesized in the same manner as inSynthesis Example 1, except that the charge ratio of the monomers werechanged.

Further, polymeric compound 4 was synthesized in the same manner as inSynthesis Example 1, except that the monomer (31) was not used.

The compositional ratios of polymeric compounds 1 to 4 (the molar ratioof the respective structural units indicated in the structural formulashown below as determined by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz ¹³C-NMR) were as follows.

Polymeric compound 1: l/m/n/o/p=30/19/18/13/19, molecular weight=7,300,dispersity=1.47

Polymeric compound 2: l/m/n/o/p=37/22/15/14/12, molecular weight=7,300,dispersity=1.39

Polymeric compound 3: l/m/n/o/p=36/26/17/14/8, molecular weight=7,200,dispersity=1.62

Polymeric compound 4: l/m/n/o/p=36/34/17/13/0, molecular weight=7,100,dispersity=1.74

Polymer Synthesis Example 5 Synthesis of Polymeric Compound 5

In a three-necked flask equipped with a thermometer and a reflux tube,25.00 g (79.1 mmol) of a compound (01), 9.69 g (27.7 mmol) of a compound(13) and 6.62 g (26.3 mmol) of a compound (32) were dissolved in 95.70 gof methyl ethyl ketone (MEK) to obtain a solution. Then, 14.4 mmol ofdimethyl 2,2′-azobis(isobutyrate) (V-601) was added and dissolved in theobtained solution. The resultant was dropwise added to 59.36 g of MEK(which had 59.36 g (266.6 mmol) of a compound (II) dissolved therein)heated to 80° C. in a nitrogen atmosphere over 3 hours. Thereafter, thereaction solution was heated for 2 hour while stirring, and then cooledto room temperature.

The obtained reaction polymer solution was dropwise added to an excessamount of n-heptane, and an operation to deposit a polymer wasconducted. Thereafter, the precipitated white powder was separated byfiltration, followed by washing with an n-heptane/2-propanol mixedsolvent and methanol in this order. The resultant was dried, therebyobtaining 44 g of a polymeric compound 5 as an objective compound.

With respect to the obtained polymeric compound, the weight averagemolecular weight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 8,300, and the dispersity was 1.68. Further, thecompositional ratio (the molar ratio of the respective structural unitsindicated in the structural formula shown below) as determined by carbon13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR) wasl/m/n/o=33.0/10.9/44.4/11.7.

Polymer Synthesis Examples 6 to 25 Synthesis of Polymeric Compounds 6 to25

Polymeric compounds 6 to 25 were synthesized in the same manner as inSynthesis Example 5, except that the charge ratio of the monomers werechanged.

The monomers used in the synthesis of polymeric compounds 5 to 25 areshown in Tables 1 to 4. Further, with respect to each of the obtainedpolymeric compounds 5 to 25, the compositional ratio (the molar ratio ofthe respective structural units indicated in the structural formulashown below) as determined by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), and the Mw and Mw/Mn determined by thepolystyrene equivalent value as measured by GPC are shown in Tables 1 to4.

TABLE 1 Polymeric compound 5 6 7 8 9 10 Mono- (21) 35.0 mer (01) 33.031.9 26.5 39.5 39.3 38.3 (11) 44.4 25.8 17.9 (12) 13.2 41.1 40.0 (13)10.9 10.3 (14) 21.6 (15) 41.4 (32) 11.7 10.4 7.4 19.1 19.6 21.7 Mw 83008200 7900 9200 9300 8100 Mw/Mn 1.68 1.74 1.78 1.52 1.51 1.58

TABLE 2 Polymeric compound 11 12 13 14 15 16 Mono- (21) 33.2 33.0 mer(22) 35.2 (23) 35.2 (24) 35.5 (25) 35.5 (01) 25.1 26.6 26.5 26.4 26.425.3 (11) 31.6 18.1 18.1 18.0 18.0 (12) 13.5 13.6 13.7 13.7 32.1 (32)10.1 5.6 6.6 6.4 6.4 9.6 Mw 7700 7600 7600 7800 7800 7800 Mw/Mn 1.691.70 1.66 1.69 1.69 1.65

TABLE 3 Polymeric compound 17 18 19 20 21 22 23 Monomer (21) 39.2 26.828.4 (01) 20.0 20.9 34.4 35.1 15.2 (02) 21.3 30.2 17.8 (11) 19.8 22.118.9 43.7 23.1 45.7 (12) 18.0 (13) 12.1 11.5 5.3 6.3 11.3 8.9 10.9 (14)40.7 23.2 (32) 7.6 19.6 8.5 19.8 13.6 9.7 10.4 Mw 7800 6200 7000 67007700 7400 7800 Mw/Mn 1.66 1.60 1.57 1.50 1.54 1.68 1.67

TABLE 4 Polymeric compound 24 25 Monomer (01) 30 35 (13) 10 10 (11) 5023 (14) 22 (31) 10 10 Mw 10000 8000 Mw/Mn 1.8 1.7

Acid Generator Synthesis Example 1 Synthesis of Compound (B)-1

5.87 g of3,5-dimethyl-4-(2-methyl-2-adamantyloxycarbonylmethyleneoxy)phenyldiphenylsulfoniumbromide, 41.85 g of dichloromethane and 20.93 g of pure water were addedto a beaker, and 4.16 g of sodium2-(1′-adamantane)carbonyloxy-1,1-difluoroethanesulfonate, followed bystirring at room temperature for 1 hour. Then, the reaction mixture wassubjected to liquid separation, and the organic phase was washed with adiluted hydrochloric acid and water in this order. The obtained organicphase was dropwise added to 249.0 g of n-hexane, thereby obtaining 6.70g of compound (B)-1 as an objective compound in the form of a whitepowder.

Acid Generator Synthesis Example 2 Synthesis of Compound (B)-2

8.2 g of a precursor (3) and 82 g of dichloromethane were added to athree-necked flask in a nitrogen atmosphere, and cooled to 5° C. orlower. Then, 0.46 g of N,N-dimethylaminopyridine (DMAP) was addedthereto, stirring was conducted at a temperature of 5° C. or lower for 5minutes, and 3.9 g of ethyl-N,N-dimethylaminopropylcarbodiimide wasadded thereto. Thereafter, stirring was conducted for 10 minutes, and4.3 g of 1-ethyl-1-cyclopentanol was added thereto. Then, thetemperature of the resultant was elevated to room temperature, andstirring was conducted at room temperature for 15 hours, followed bywashing with a diluted hydrochloric acid and pure water in this order.The resulting organic phase was dropwise added to 1,000 g of n-hexaneand precipitated, thereby obtaining 5.0 g of a precursor (4).

Subsequently, the obtained precursor (4) was subjected to a saltexchange reaction with a compound (4) which was synthesized inaccordance with the description in paragraph [0487] of US Pre-GrantPublication No. 2009-0130597, thereby obtaining a compound (B)-2.

Production of Positive Resist Composition Test Examples 1 to 12

The components shown in Table 5 were mixed together and dissolved toobtain positive resist compositions. With respect to Test Examples 1 to12, Test Examples 1 to 3 and 5 to 12 are examples of the presentinvention, and Test Example 4 is a comparative example.

TABLE 5 Component Component Component (A) (B) (D) Component (S) Test(A)-1 (B)-1 (D)-1 (S)-1 (S)-2 Example 1 [100]  [9.8] [0.5]  [2000] [10]Test (A)-2 (B)-1 (D)-1 (S)-1 (S)-2 Example 2 [100]  [9.8] [0.5]  [2000][10] Test (A)-3 (B)-1 (D)-1 (S)-1 (S)-2 Example 3 [100]  [9.8] [0.5] [2000] [10] Test (A)-4 (B)-1 (D)-1 (S)-1 (S)-2 Example 4 [100]  [9.8][0.5]  [2000] [10] Test (A)-5 (B)-1 (D)-1 (S)-1 (S)-2 Example 5 [100] [9.8] [0.5]  [2000] [10] Test (A)-5 (B)-2 (D)-1 (S)-1 (S)-2 Example 6[100] [10.5] [0.21] [2400] [10] Test (A)-6 (B)-2 (D)-1 (S)-1 (S)-2Example 7 [100] [10.5] [0.21] [2400] [10] Test (A)-7 (B)-2 (D)-1 (S)-1(S)-2 Example 8 [100] [10.5] [0.21] [2400] [10] Test (A)-8 (B)-2 (D)-1(S)-1 (S)-2 Example 9 [100] [10.5] [0.21] [2400] [10] Test (A)-9 (B)-2(D)-1 (S)-1 (S)-2 Example 10 [100] [10.5] [0.21] [2400] [10] Test (A)-6(A)-7 (B)-2 (D)-1 (S)-1 (S)-2 Example 11  [50] [50] [10.5] [0.21] [2400][10] Test (A)-8 (A)-9 (B)-2 (D)-1 (S)-1 (S)-2 Example 12  [50] [50][10.5] [0.21] [2400] [10] In Table 5, the reference characters indicatethe following. Further, the values in brackets [ ] indicate the amount(in terms of parts by weight) of the component added. (A)-1: theaforementioned polymeric compound 1 (amount of structural unit (a3): 19mol %) (A)-2: the aforementioned polymeric compound 2 (amount ofstructural unit (a3): 12 mol %) (A)-3: the aforementioned polymericcompound 3 (amount of structural unit (a3): 8 mol %) (A)-4: theaforementioned polymeric compound 4 (amount of structural unit (a3): 0mol %) (A)-5: the aforementioned polymeric compound 7 (amount ofstructural unit (a3): 7.8 mol %) (A)-6: the aforementioned polymericcompound 5 (amount of structural unit (a3): 10 mol %) (A)-7: theaforementioned polymeric compound 6 (amount of structural unit (a3):10.4 mol %) (A)-8: the aforementioned polymeric compound 24 (amount ofstructural unit (a3): 10 mol %) (A)-9: the aforementioned polymericcompound 25 (amount of structural unit (a3): 10 mol %) (B)-1: theaforementioned compound (B)-1 (B)-2: the aforementioned compound (B)-2(D)-1: tri-n-pentylamine (S)-1: a mixed solvent of PGMEA/PGME = 6/4(weight ratio) (S)-2: γ-butyrolactone

Using the obtained positive resist compositions, the heat resistance wasevaluated as follows.

<Evaluation of Heat Resistance 1: Trench Pattern>

Each of the positive resist compositions of Test Examples 1 to 5 wasapplied to an 8-inch silicon substrate which had been treated (90° C.for 36 seconds) with hexamethyldisilazane (HMDS), and prebaked (postapplied bake (PAB)) on a hot plate at 90° C. for 60 seconds and dried,thereby forming a resist film having a film thickness of 200 nm.Subsequently, the resist film was selectively irradiated with an ArFexcimer laser (193 nm) through a mask pattern, using an ArF exposureapparatus NSR-S302 (manufactured by Nikon Corporation, NA (numericalaperture)=0.60, σ=0.75). Thereafter, a post exposure bake (PEB)treatment was conducted at 85° C. for 60 seconds, followed bydevelopment for 30 seconds at 23° C. in a 2.38% by weight aqueoussolution of tetramethylammonium hydroxide (TMAH). Then, the resist waswashed for 15 seconds with pure water. As a result, a trench patternhaving a space width of 300 nm was formed on each of the resist films.

The thus formed trench pattern was subjected to a post bake treatment ata predetermined temperature (140° C., 160° C. or 180° C.) for 60seconds. Then, each trench pattern after the post bake treatment wasobserved from the upper side thereof using a scanning electronmicroscope, and the space width (nm) was measured.

As a result, in Test Examples 1 to 3 and 5, almost no influence wasnoted after the post bake treatment at 140° C. In Test Example 4, thespace width became slightly small.

After the post bake treatment at 160° C., almost no influence was notedin Test Examples 1 and 2, and the spate width became slightly small inTest Example 3. In Test Example 4, the pattern was completely filled.

After the post bake treatment at 180° C., the space width became smallin all of Test Examples 1 to 5. However, the change in size was smalleras the amount of the structural unit (a3) became larger. The space widthof each example after the post bake treatment at 180° C. are shown inTable 6.

TABLE 6 Space width of trench pattern After post bake Prior to post bake(180° C.) Test 300 nm 289 nm Example 1 Test 300 nm 244 nm Example 2 Test300 nm 197 nm Example 3 Test 300 nm  0 nm Example 4 Test 300 nm 159 nmExample 5

<Evaluation of Heat Resistance 2: Hole Pattern>

Isolated patterns having a hole diameter of 300 nm were formed in thesame manner as in the “evaluation of heat resistance 1”, except that themask pattern was changed.

The thus formed hole patterns were subjected to a post bake treatment ata predetermined temperature (100° C. to 170° C., at intervals of 10° C.)for 60 seconds. Then, each hole pattern after the post bake treatmentwas observed from the upper side thereof using a scanning electronmicroscope, and the size (diameter) (nm) of the hole pattern wasmeasured.

As a result, in Test Examples 1 to 5, almost no influence was notedafter the post bake treatment at 100 to 140° C.

After the post bake treatment at 150 to 160° C., almost no influence wasnoted in Test Examples 1 and 2, and the size of the hole pattern becameslightly small in Test Examples 3 and 5. In Test Example 4, the size ofthe hole pattern became smaller than those of Test Examples 1 to 3 and5.

After the post bake treatment at 170° C., the size of the hole patternbecame small in all of Test Examples 1 to 5. However, the change in sizewas smaller as the amount of the structural unit (a3) became larger. Thesize of the hole pattern for each example after the post bake treatmentat 170° C. are shown in Table 7.

TABLE 7 Size of hole pattern After post bake Prior to post bake (170°C.) Test 300 nm 292 nm Example 1 Test 300 nm 261 nm Example 2 Test 300nm 205 nm Example 3 Test 300 nm  0 nm Example 4 Test 300 nm 185 nmExample 5

From the results shown above, it was confirmed that the larger theamount of the structural unit (a3) within the component (A1), the higherthe heat resistance of a positive resist composition containing thepolymeric compound, and change in size of the resist pattern caused by abaking treatment was less likely to occur.

<Evaluation of Lithography Properties 1>

Using the resist compositions obtained in Test Examples 1 to 4, resistpatterns were formed in the following manner, and the lithographyproperties were evaluated.

[Formation of Resist Pattern; Contact Hole Pattern]

An organic anti-reflection film composition (product name: ARC29A,manufactured by Brewer Science Ltd.) was applied to an 12-inch siliconwafer using a spinner, and the composition was then baked at 205° C. for60 seconds, thereby forming an organic anti-reflection film having afilm thickness of 89 nm. Then, each of the resist compositions obtainedabove was applied to the anti-reflection film using a spinner, and wasthen prebaked (PAB) on a hotplate at 100° C. for 60 seconds and dried,thereby forming a resist film having a film thickness of 120 nm.

Subsequently, a coating solution for forming a protection film (productname: TILC-035; manufactured by Tokyo Ohka Kogyo Co., Ltd.) was appliedto the resist film using a spinner, and then heated at 90° C. for 60seconds, thereby forming a top coat with a film thickness of 35 nm.

Thereafter, using an ArF exposure apparatus for immersion lithography(product name: NSR-5609B, manufactured by Nikon Corporation, NA(numerical aperture)=1.07, σ0.97), the resist film having a top coatformed thereon was selectively irradiated with an ArF excimer laser (193nm) through a mask pattern for forming a hole pattern.

Thereafter, a post exposure bake (PEB) treatment was conducted at 95° C.for 60 seconds, followed by alkali development for 30 seconds at 23° C.in a 2.38% by weight aqueous solution of tetramethylammonium hydroxide(TMAH) (product name: NMD-W; manufactured by Tokyo Ohka Kogyo Co.,Ltd.). Then, the resist was washed for 25 seconds with pure water,followed by drying by shaking.

As a result, in each of the examples, a contact hole pattern in whichholes having a diameter of 70 nm were equally spaced (pitch: 122.5 nm)was formed on the resist film (hereafter, this contact hole pattern isreferred to as “dense CH pattern”).

[Evaluation of in-Plane Uniformity]

The dense CH patterns formed above were observed using a scanningelectron microscope (SEM) (product name: S-9220, manufactured byHitachi, Ltd.). As a result, in Test Example 4, it was observed that apart of the pattern was covered, and fluctuation in the in-plane patternsize was noted. On the other hand, in Test Examples 1 to 3, suchfluctuation was not noted. The reason for this is presumed that byintroducing the structural unit (a3), diffusion of the acid generatedfrom the component (B) can be appropriately suppressed, and EL margin isimproved, thereby suppressing the fluctuation of the in-plane size.

<Evaluation of Lithography Properties 2>

Using the resist compositions obtained in Test Examples 6 to 12, resistpatterns were formed in the following manner, and the lithographyproperties were evaluated.

[Formation of Resist Pattern]

An organic anti-reflection film composition (product name: ARC29,manufactured by Brewer Science Ltd.) was applied to a 12-inch siliconwafer using a spinner, and the composition was then baked at 205° C. for60 seconds, thereby forming an organic anti-reflection film having afilm thickness of 89 nm. Then, each of the resist compositions obtainedabove was applied to the anti-reflection film using a spinner, and wasthen prebaked (PAB) on a hotplate at 90° C. for 60 seconds and dried,thereby forming a resist film having a film thickness of 100 nm.

Subsequently, a coating solution for forming a protection film (productname: TILC-057; manufactured by Tokyo Ohka Kogyo Co., Ltd.) was appliedto the resist film using a spinner, and then heated at 90° C. for 60seconds, thereby forming a top coat with a film thickness of 35 nm.

Thereafter, using an ArF immersion exposure apparatus (product name:NSR-S609B, manufactured by Nikon Corporation, NA (numericalaperture)=1.07, σ0.97), the resist film having a top coat formed thereonwas selectively irradiated with an ArF excimer laser (193 nm) through amask pattern for forming a hole pattern.

Thereafter, a post exposure bake (PEB) treatment was conducted at 80° C.for 60 seconds, followed by alkali development for 30 seconds at 23° C.in a 2.38% by weight aqueous solution of tetramethylammonium hydroxide(TMAH) (product name: NMD-3; manufactured by Tokyo Ohka Kogyo Co.,Ltd.). Then, the resist was washed for 25 seconds with pure water,followed by drying by shaking. Further, a post bake treatment wasconducted at 100° C. for 45 seconds.

As a result, in each of the examples, a contact hole pattern in whichholes having a diameter of 85 nm were equally spaced (pitch: 140 nm) wasformed on the resist film (hereafter, this contact hole pattern isreferred to as “CH pattern”).

[Evaluation of Mask Reproducibility]

Using the optimum exposure dose with which the above CH pattern wasformed, CH patterns were formed using a mask pattern (the pitch fixed at140 nm) targeting a hole diameter of 81 nm to 88 nm (8 targets atintervals of 1 nm). The value of the mask error factor was determined asthe gradient of a graph obtained by plotting the target size (nm) on thehorizontal axis, and the actual hole diameter (nm) of the formed CHpatterns on the vertical axis. The mask reproducibility was evaluated inaccordance with the following criteria. The results are shown in Table8. A MEF value (gradient of the plotted line) closer to 1 indicates thata resist pattern faithful to the mask pattern was formed.

(Criteria)

A: MEF is 4 or more and less than 4.5

B: MEF is 4.5 or more and less than 5.0

TABLE 8 Mask reproducibility Test A Example 6 Test A Example 7 Test AExample 8 Test B Example 9 Test B Example 10 Test A Example 11 Test BExample 12

From the results shown above, it was found that the MEF can be improvedby using a specific amount of the structural unit (a3) within thecomponent (A1).

While preferred embodiments of the invention have been described andillustrated above, it should be understood that these are exemplary ofthe invention and are not to be considered as limiting. Additions,omissions, substitutions, and other modifications can be made withoutdeparting from the spirit or scope of the present invention.Accordingly, the invention is not to be considered as being limited bythe foregoing description, and is only limited by the scope of theappended claims.

What is claimed is:
 1. A polymeric compound comprising: a structuralunit (a0) represented by general formula (a0-1) shown below, astructural unit (a1) derived from an acrylate ester containing an aciddissociable, dissolution inhibiting group, and a structural unit (a3)derived from an acrylate ester containing a hydroxy group-containingaliphatic hydrocarbon group represented by general formula (a3-1) shownbelow, wherein an amount of the structural unit (a3) based on a combinedtotal of all structural units constituting the polymeric compound (A1)is in a range of 1 to 30 mol %:

in formula (a0-1), R represents a hydrogen atom, an alkyl group of 1 to5 carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms, R²represents a divalent linking group, and R³ represents a cyclic groupcontaining —SO₂— within the ring skeleton thereof; and in formula(a3-1), R represents a hydrogen atom, an alkyl group of 1 to 5 carbonatoms or a halogenated alkyl group of 1 to 5 carbon atoms; each ofR_(a), R_(b) and R_(c) independently represents a hydrogen atom, analkyl group of 1 to 5 carbon atoms, a hydroxy group or a hydroxyalkylgroup, provided that at least one of R_(a), R_(b) and R_(c) represents ahydroxy group or a hydroxyalkyl group; and R_(d) represents a singlebond or a divalent linking group.
 2. The polymeric compound according toclaim 1, wherein R³ represents a cyclic group containing —O—SO₂— withinthe ring skeleton thereof.
 3. The polymeric compound according to claim2, wherein R³ is a cyclic group represented by general formula (3-1)shown below:

wherein A′ represents an oxygen atom, a sulfur atom, or an alkylenegroup of 1 to 5 carbon atoms which may contain an oxygen atom or asulfur atom; a represents an integer of 0 to 2; and R⁶ represents analkyl group, an alkoxy group, a halogenated alkyl group, a hydroxylgroup, —COOR″, —OC(═O)R″, a hydroxyalkyl group or a cyano group, whereinR″ represents a hydrogen atom or an alkyl group.
 4. The polymericcompound according to claim 1, wherein the structural unit (a1)comprises at least two types of structural units.
 5. The polymericcompound according to claim 1, wherein the structural unit (a1)comprises at least one member selected from the group consisting of astructural unit represented by general formula (a1-0-11) shown below, astructural unit represented by general formula (a1-0-12) shown below anda structural unit represented by general formula (a1-0-2) shown below:

wherein R represents a hydrogen atom, an alkyl group of 1 to 5 carbonatoms or a halogenated alkyl group of 1 to 5 carbon atoms; R²¹represents an alkyl group; R²² represents a group which forms analiphatic monocyclic group with the carbon atom to which R²² is bonded;R²³ represents a branched alkyl group; R²⁴ represents a group whichforms an aliphatic polycyclic group with the carbon atom to which R²⁴ isbonded; Y² represents a divalent linking group; and X² represents anacid dissociable, dissolution inhibiting group.
 6. The polymericcompound according to claim 1, which further comprises a structural unit(a2) derived from an acrylate ester containing a lactone-containingcyclic group.